refactor(map): enhanced implementation, Clean Code™, etc etc

This involves two redesigns of the map.c implementations:

1. Change of macro style and code organization

The old khash.h and map.c implementation used huge #define blocks with a
lot of backslash line continuations.

This instead uses the "implementation file" .c.h pattern. Such a file is
meant to be included multiple times, with different macros set prior to
inclusion as parameters. we already use this pattern e.g. for
eval/typval_encode.c.h to implement different typval encoders reusing a
similar structure.

We can structure this code into two parts. one that only depends on key
type and is enough to implement sets, and one which depends on both key
and value to implement maps (as a wrapper around sets, with an added
value[] array)

2. Separate the main hash buckets from the key / value arrays

Change the hack buckets to only contain an index into separate key /
value arrays
This is a common pattern in modern, state of the art hashmap
implementations. Even though this leads to one more allocated array, it
is this often is a net reduction of memory consumption. Consider
key+value consuming at least 12 bytes per pair. On average, we will have
twice as many buckets per item.
Thus old implementation:

  2*12 = 24 bytes per item

New implementation

  1*12 + 2*4 = 20 bytes per item

And the difference gets bigger with larger items.
One might think we have pulled a fast one here, as wouldn't the average size of
the new key/value arrays be 1.5 slots per items due to amortized grows?
But remember, these arrays are fully dense, and thus the accessed memory,
measured in _cache lines_, the unit which actually matters, will be the
fully used memory but just rounded up to the nearest cache line
boundary.

This has some other interesting properties, such as an insert-only
set/map will be fully ordered by insert only. Preserving this ordering
in face of deletions is more tricky tho. As we currently don't use
ordered maps, the "delete" operation maintains compactness of the item
arrays in the simplest way by breaking the ordering. It would be
possible to implement an order-preserving delete although at some cost,
like allowing the items array to become non-dense until the next rehash.

Finally, in face of these two major changes, all code used in khash.h
has been integrated into map.c and friends. Given the heavy edits it
makes no sense to "layer" the code into a vendored and a wrapper part.
Rather, the layered cake follows the specialization depth: code shared
for all maps, code specialized to a key type (and its equivalence
relation), and finally code specialized to value+key type.

1 files changed, 9 insertions, 9 deletions

diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 891c81d470..70c97be984 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -136,7 +136,7 @@ void remote_ui_wait_for_attach(void)
   }
 
   LOOP_PROCESS_EVENTS_UNTIL(&main_loop, channel->events, -1,
-                            pmap_has(uint64_t)(&connected_uis, CHAN_STDIO));
+                            map_has(uint64_t, &connected_uis, CHAN_STDIO));
 }
 
 /// Activates UI events on the channel.
@@ -158,7 +158,7 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height, Dictiona
                     Error *err)
   FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
 {
-  if (pmap_has(uint64_t)(&connected_uis, channel_id)) {
+  if (map_has(uint64_t, &connected_uis, channel_id)) {
     api_set_error(err, kErrorTypeException,
                   "UI already attached to channel: %" PRId64, channel_id);
     return;
@@ -233,7 +233,7 @@ void ui_attach(uint64_t channel_id, Integer width, Integer height, Boolean enabl
 void nvim_ui_set_focus(uint64_t channel_id, Boolean gained, Error *error)
   FUNC_API_SINCE(11) FUNC_API_REMOTE_ONLY
 {
-  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+  if (!map_has(uint64_t, &connected_uis, channel_id)) {
     api_set_error(error, kErrorTypeException,
                   "UI not attached to channel: %" PRId64, channel_id);
     return;
@@ -255,7 +255,7 @@ void nvim_ui_set_focus(uint64_t channel_id, Boolean gained, Error *error)
 void nvim_ui_detach(uint64_t channel_id, Error *err)
   FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
 {
-  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+  if (!map_has(uint64_t, &connected_uis, channel_id)) {
     api_set_error(err, kErrorTypeException,
                   "UI not attached to channel: %" PRId64, channel_id);
     return;
@@ -271,7 +271,7 @@ void remote_ui_stop(UI *ui)
 void nvim_ui_try_resize(uint64_t channel_id, Integer width, Integer height, Error *err)
   FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
 {
-  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+  if (!map_has(uint64_t, &connected_uis, channel_id)) {
     api_set_error(err, kErrorTypeException,
                   "UI not attached to channel: %" PRId64, channel_id);
     return;
@@ -292,7 +292,7 @@ void nvim_ui_try_resize(uint64_t channel_id, Integer width, Integer height, Erro
 void nvim_ui_set_option(uint64_t channel_id, String name, Object value, Error *error)
   FUNC_API_SINCE(1) FUNC_API_REMOTE_ONLY
 {
-  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+  if (!map_has(uint64_t, &connected_uis, channel_id)) {
     api_set_error(error, kErrorTypeException,
                   "UI not attached to channel: %" PRId64, channel_id);
     return;
@@ -426,7 +426,7 @@ void nvim_ui_try_resize_grid(uint64_t channel_id, Integer grid, Integer width, I
                              Error *err)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY
 {
-  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+  if (!map_has(uint64_t, &connected_uis, channel_id)) {
     api_set_error(err, kErrorTypeException,
                   "UI not attached to channel: %" PRId64, channel_id);
     return;
@@ -448,7 +448,7 @@ void nvim_ui_try_resize_grid(uint64_t channel_id, Integer grid, Integer width, I
 void nvim_ui_pum_set_height(uint64_t channel_id, Integer height, Error *err)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY
 {
-  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+  if (!map_has(uint64_t, &connected_uis, channel_id)) {
     api_set_error(err, kErrorTypeException,
                   "UI not attached to channel: %" PRId64, channel_id);
     return;
@@ -489,7 +489,7 @@ void nvim_ui_pum_set_bounds(uint64_t channel_id, Float width, Float height, Floa
                             Error *err)
   FUNC_API_SINCE(7) FUNC_API_REMOTE_ONLY
 {
-  if (!pmap_has(uint64_t)(&connected_uis, channel_id)) {
+  if (!map_has(uint64_t, &connected_uis, channel_id)) {
     api_set_error(err, kErrorTypeException,
                   "UI not attached to channel: %" PRId64, channel_id);
     return;