refactor(sign): move legacy signs to extmarks

Problem:  The legacy signlist data structures and associated functions are
          redundant since the introduction of extmark signs.
Solution: Store signs defined through the legacy commands in a hashmap, placed
          signs in the extmark tree. Replace signlist associated functions.

Usage of the legacy sign commands should yield no change in behavior with the
exception of:
  - "orphaned signs" are now always removed when the line it is placed on is
    deleted. This used to depend on the value of 'signcolumn'.
  - It is no longer possible to place multiple signs with the same identifier
    in a single group on multiple lines. This will now move the sign instead.

Moreover, both signs placed through the legacy sign commands and through
|nvim_buf_set_extmark()|:
  - Will show up in both |sign-place| and |nvim_buf_get_extmarks()|.
  - Are displayed by increasing sign identifier, left to right.
    Extmark signs used to be ordered decreasingly as opposed to legacy signs.

1 files changed, 0 insertions, 6 deletions

diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index 9ca1396753..c5dfa91f27 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -7590,12 +7590,6 @@ return {
                         number (maximum 9), e.g. "yes:3"
            "number"	display signs in the 'number' column. If the number
         		column is not present, then behaves like "auto".
-
-        Note regarding "orphaned signs": with signcolumn numbers higher than
-        1, deleting lines will also remove the associated signs automatically,
-        in contrast to the default Vim behavior of keeping and grouping them.
-        This is done in order for the signcolumn appearance not appear weird
-        during line deletion.
       ]=],
       expand_cb = 'expand_set_signcolumn',
       full_name = 'signcolumn',