perf thread_map: Reduce exposure of libperf internal API

perf thread_map: Reduce exposure of libperf internal API

Remove unnecessary include of internal threadmap.h and refcount.h in
thread_map.h. Switch to using public APIs when possible or including
the internal header file in the C file. Fix a transitive dependency in
openat-syscall.c broken by the clean up.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: bpf@vger.kernel.org
Link: http://lore.kernel.org/lkml/20221109184914.1357295-13-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>