The benefits are primarily being able to use FetchContent, which allows
for a more flexible dependency handling. Other various quality-of-life
features such as `-B` and `-S` flags are also included.
This also removes broken `--version` generation as it does not work for
version 3.10 and 3.11 due to the `JOIN` generator expression.
Reference: https://github.com/neovim/neovim/issues/24004
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/)
