perf report: Display pregress bar on redirected pipe data

It's possible to save pipe output of perf record into a file.

  $ perf record -o- ... > pipe.data

And you can use the data same as the normal perf data.

  $ perf report -i pipe.data

In that case, perf tools will treat the input as a pipe, but it can get
the total size of the input.  This means it can show the progress bar
unlike the normal pipe input (which doesn't know the total size in
advance).

While at it, fix the string in __perf_session__process_dir_events().

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240627181916.1202110-1-namhyung@kernel.org