rohks 76310ad40c Add timestamp to Metadata
`MetadataRenderer` is updated to output `Metadata` with its presentation time, in microseconds.

PiperOrigin-RevId: 457444718
(cherry picked from commit 6e9275c13d7c6e0fc8b6568662929c186395a33a)
2022-06-27 11:31:10 +00:00
..
2022-06-27 11:31:10 +00:00