Add debug messages to enable scripts to track aspects of 'perf record'
behaviour. The messages will be consumed after 'perf record' has run,
with the exception of "perf record has started" which is consequently
flushed.

Put comments so developers know which messages are also being used by test
scripts.
Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
Acked-by: NNamhyung Kim <namhyung@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220912083412.7058-11-adrian.hunter@intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>