transcoding: Address API council comments.

1. Add new API isFormatSpecified to query if client has specified the
format.
2. Remove the FormatNotFoundException for the APIs.

Bug: 179727499
Test: atest  CtsMediaTranscodingTestCases:ApplicationMediaCapabilitiesTest
Change-Id: Ifb2b990f1bce3e6aeb3c4e11b82b08a548c7173e
3 files changed