tools/rtla: Add basic test suite

Implement a simple TAP-based test engine in bash and a few basic tests
using it, to be used to check for bugs and regressions.

A new "check" target is added to the rtla Makefile that runs the test suite
using the "prove" command implemented by Test::Harness.

The only test format currently supported is running rtla with defined
command arguments per test, checking its exit code. In case the exit
code is non-zero, the output of rtla is displayed, together with the
exit code.

The test cases are adopted from rtla tests in the Continuous Kernel
Integration (CKI) project [1] with the authors' approval.

[1] https://gitlab.com/redhat/centos-stream/tests/kernel/kernel-tests/-/blob/main/rt-tests/us/rtla/

Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Cc: Chang Yin <cyin@redhat.com>
Cc: Qiao Zhao <qzhao@redhat.com>
Link: https://lore.kernel.org/20250120135630.802111-1-tglozar@redhat.com


Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>