perf sched: Commit to evsel__taskstate() to parse task state info

perf sched: Commit to evsel__taskstate() to parse task state info

Now that we have evsel__taskstate() which no longer relies on the
hardcoded task state string and has good backward compatibility,
we have a good reason to use it.

Note TASK_STATE_TO_CHAR_STR and task bitmasks are useless now so
we remove them for good. And now we pass the state info back and
forth in a symbolic char which explains itself well instead.

Signed-off-by: Ze Gao <zegao@tencent.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20240123022425.1611483-1-zegao@tencent.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>