* 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()

Using the std option, so now `rust_std=..` will work. I've chosen to use
"std" even though rust calls these "editions", as meson refers to
language versions as "standards", which makes meson feel more uniform,
and be less surprising.

Fixes: #5100

This fix a regression caused by
https://github.com/mesonbuild/meson/pull/7837, it wanted to make
InternalDependency's external_deps private but has side effect of making
StatisLibrary's external_deps private too.

It is technically correct to make them private, but Meson used to make
StaticLibrary deps public so they are usable without `pkg-config
--static` when we know there is only a static library available.

Fixes: #7929.

Fixes #7925