selftests/bpf: Add tracing multi attach rollback tests

selftests/bpf: Add tracing multi attach rollback tests

Adding tests for the rollback code when the tracing_multi
link won't get attached, covering 2 reasons:

  - wrong btf id passed by user, where all previously allocated
    trampolines will be released
  - trampoline for requested function is fully attached (has already
    maximum programs attached) and the link fails, the rollback code
    needs to release all previously link-ed trampolines and release
    them

We need the bpf_fentry_test* unattached for the tests to pass,
so the rollback tests are serial.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-30-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>