perf trace: Convert syscall_stats to hashmap

perf trace: Convert syscall_stats to hashmap

It was using a RBtree-based int-list as a hash and a custom resort
logic for that.  As we have hashmap, let's convert to it and add a
custom sort function for the hashmap entries using an array.  It
should be faster and more light-weighted.  It's also to prepare
supporting system-wide syscall stats.

No functional changes intended.

Reviewed-by: Howard Chu <howardchu95@gmail.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20250205205443.1986408-3-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>