Problem:
Dirs "config", "packaging", and "third-party" are all closely related
but this is not obvious from the layout. This adds friction for new
contributors.

Solution:
- rename config/ to cmake.config/
- rename test/config/ to test/cmakeconfig/ because it is used in Lua
  tests: require('test.cmakeconfig.paths').
- rename packaging/ to cmake.packaging/
- rename third-party/ to cmake.deps/ (parallel with .deps/)

Problem
- `redir_exec` is obsolete, but it keeps getting used in new tests
  because people copy existing tests.
- Disadvantages of `redir_exec`:
  - Captures extra junk before the actual error/message that we _want_ to test.
  - Does not fail on error, unlike e.g. `command()`.

Solution
- Use new functions like `nvim_exec` and `pcall_err`.

As Strings and Blobs are encoded as msgpack BINs, the current ShaDa
implementation will restore global Blob variables as Strings (or msgpack
special dicts if they contain NULs).

Encode an additional element with Blob globals to differentiate them
from Strings so that we can restore them with the correct type.

Adjust variables_spec.lua's autotest() to also check for proper type.

If set the number of history saves is 0, assertions fail when inserting an entry on exit.
Dont insert an entry when the number of saves is 0 fixes the issue.

fixes #11497

Problem:    Writing viminfo fails with a circular reference.
Solution:   Use copyID to detect the cycle. (closes vim/vim#6217)
https://github.com/vim/vim/commit/5b157fe2edfdce5f77080aeac2b4a03f39eb1c1a

Fix the problem of failing to write shada when the global variable contains
Funcref or Partial.

Since 8b8ecf4, the shada module loads files in the jumplist to properly
clear duplicates. This can trigger some autocommands, which in turn
saves and restores search and substitute patterns, freeing the previous
strings in "spats" which are held in "wms" as well (heap-use-after-free).
To avoid this, initialize the jumplist in "wms" before search patterns.