Fixes #8068.

There is no reason why meson should swallow any non-zero exit(/return)
code of clang-format.

It turns out my first attempt to fix this in 00d5ef3191e5 ("Fix
clang-tidy return value reporting (#7949)") is not sufficient: The
local variable returncode is never updated and stays at 0. This fixes
the returncode calculation.

Fixes: cce172432be3 ("Use run-clang-tidy when available.")

* 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