tests: posix: headers: remove testsuite

Remove the tests/posix/headers testsuite.

A large part of this testsuite was originally feeling-out what types,
functions, and other declarations were expected in POSIX headers when
CONFIG_POSIX_API was not selected.

Really, libraries and applications should generally not expect to be able
to use POSIX headers in particularly meaningful ways when POSIX APIs are
not enabled.

The portions of the testsuite that check for the existence of declarations
and symbols when POSIX APIs are configured also effectively duplicates
the implicit tests of simply compiling code and testsuites.

Also, given that CONFIG_POSIX_API is effectively deprecated, it does not
make a lot of sense to maintain the testsuite.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>
27 files changed