libperf: Add perf_thread_map__new_dummy() function

libperf: Add perf_thread_map__new_dummy() function

Moving the following functions:

  thread_map__new_dummy()
  thread_map__realloc()
  thread_map__set_pid()

to libperf with the following names:

  perf_thread_map__new_dummy()
  perf_thread_map__realloc()
  perf_thread_map__set_pid()

the other 2 functions are dependencies of the
perf_thread_map__new_dummy() function.

The perf_thread_map__realloc() function is not exported.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190721112506.12306-33-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>