* Fix clang-tidy return value reporting

In case clang-tidy is invoked manually, i.e. if run-clang-tidy(.py) is
not found, Meson would not report the return value. This is caused by
ignoring the return value of manual_clangformat() in clangformat()
within mesonbuild/scripts/clangtidy.py.

Even though only more recent-versions of clang-tidy actually report an
non-zero exit code if errors are found, there is no reason Meson
shouldn't simply report any error codes it received from clang-tidy.

Fixes #7948.

* Rename methods in clangtidy.py from clangformat to clangtidy

For some unknown reason, the method names in clangtidy.py are clangformat()
and manual_clangformat(). This is confusing, as clang-format is not
invoked by them, clang-tidy is. Hence rename those from

{manual_}clangformat() → {manual_}clangtidy()

* fix 5492 with cleaner code

* remove argparse import

* replace list(map( with list comprehension

* pass str rather than Path to get_cmd_line_file

by default run_clang_tidy process al file in compile_commands.json but
the file generated has to be esclude like already done from
manual_clangformat

`pathlib.Path.glob()` also returns directories that match source
filenames (i.e. a directory named `test.h/`), but `clang-format` and
`clang-tidy` fail when handed a directory. We manually skip calling
`clang-format` and `clang-tidy` on those directories.

Make 'meson --internal exe --unpickle' report the actual command
executed when it fails, which is otherwise invisible.

This adds an experimental meson module to build projects with other
build systems.

Closes: #4316