Fix remaining clint errors and remove error suppression completely.

Rename the lint targets to align with the established naming convention:

- lintc-clint lints with clint.py.
- lintc-uncrustify lints with uncrustify.
- lintc runs both targets.

lintc is also provided as a make target for convenience.

After this change we can remove these files:
https://github.com/neovim/doc/tree/gh-pages/reports/clint
https://github.com/neovim/doc/blob/main/ci/clint-errors.sh

Replace old-school cmake with the so-called "Modern CMake", meaning
preferring using targets and properties over directory settings and
variables. This allows greater flexibility, robustness and clarity over
how the code works.

The following deprecated commands will be replaced with their modern
alternatives that operates on a specific target, rather than all targets
in the current directory:

- add_compile_options -> target_compile_options
- include_directories -> target_include_directories
- link_libraries -> target_link_libraries
- add_definitions -> target_compile_definitions

There are mainly four main targets that we currently use: nvim, libnvim,
nvim-test (used by unittests) and ${texe} (used by
check-single-includes). The goal is to explicitly define the
dependencies of each target fully, rather than having everything be
dependent on everything else.

fix version determination when building neovim from release tarball
extracted within another git repository

build: add more shell scripts to the `lintsh` target

EXCLUDE filters out all elements containing regex, meaning it works on
both files and directories.

Also rename add_glob_targets to add_glob_target since only one target is
being created.

This is just to allow the reader to get a quick understanding without
necessarily needing to know all the regex intricasies.

- Prevent duplicate version strings such as v0.8.0-v0.8.0.
- Change the format for git releases from v0.9.0-dev-67-g625ba79be to
  v0.9.0-dev-67+g625ba79be.

Nvim versions are now:
release                    : v0.9.0
prerelease without git info: v0.9.0-dev
prerelease with git info   : v0.9.0-dev-67+g625ba79be

The environment variable CIRRUS_CI is manually passed to RunTests.cmake
as it doesn't get passed when using cmake script mode.

The commands run in cmake script mode (-P) can simply be run in the main
cmake run instead.

It was set in file cmake/i386-linux-gnu.toolchain.cmake which has been
removed since we don't use Travis anymore.