add MediaCodec XML minsdk=# attribute

Add a minsdk="#" attribute to the MediaCodec XML clause. This supports
the idea of a codec distributed via mainline but enabled only on certain
Android releases.

Bug: 242057615
Test: enable/minsdk combinations on Q/R/S/T/master devices
Test: atest XMLParserTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:9c362b60eef6f51434e33385703871a795715d18)
Merged-In: I708aa6dcd49cf06fdab011e6611551c482027ebf
Change-Id: I708aa6dcd49cf06fdab011e6611551c482027ebf