meson: Annotate each test() with 'suite'

A test case can be part of a test suite (just like we already
have 'syntax-check'). This then allows developers to run only a
subset of tests. For instance - when using valgrind test setup
(`meson test -C _build/ --setup valgrind`) it makes zero sense to
run syntax-check tests or other script based tests (e.g.
check-augeas-*, check-remote_protocol, etc.). What does makes
sense is to run compiled binaries.

Strictly speaking, reaching that goal is as trivial as annotating
only those compiled tests (declared in tests/meson.build) and
running them selectively:

  meson test -C _build/ --setup valgrind --suite $TAG

But it may be also desirable to run test scripts separately.

Therefore, introduce two new tags: 'bin' for compiled tests, and
'script' for script based tests and annotate each test()
accordingly.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

docs/advanced-tests.rst

@@ -16,7 +16,7 @@ by running
 
 ::
 
-  $ meson test --setup valgrind
+  $ meson test --setup valgrind --suite bin
 
 `Valgrind <https://valgrind.org/>`__ is a test that checks for
 memory management issues, such as leaks or use of uninitialized