Align CryptoInfo value and identity equality

CryptoInfo.pattern is private, so users need to ensure
CryptoInfo instances do not change between being obtained
from MediaParser, and being passed to MediaCodec. This CL
ensures that MediaParser does not modify any already output
CryptoInfo instances.

Bug: 154120292
Test: manually.
Test: atest CtsMediaParserTestCases.
Change-Id: I800b6e6ae98af490e5001a5da35cae5d3b8449e6