perf data: Implement 'index' subcommand

The index command first splits a given data file into intermediate
data files and merges them into a final data file with an index table
so that it can processed using multi threads.  The HEADER_DATA_INDEX
feature bit is added to distinguish data file that has an index table.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2 files changed