selftests/rseq: Expand for optimized RSEQ ABI v2

selftests/rseq: Expand for optimized RSEQ ABI v2

Update the selftests so they are executed for legacy (32 bytes RSEQ region)
and optimized RSEQ ABI v2 mode.

Fixes: d6200245c75e ("rseq: Allow registering RSEQ with slice extension")
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Link: https://patch.msgid.link/20260428224428.009121296%40kernel.org
Cc: stable@vger.kernel.org