ultrahdr: rework jpegr unit tests

- Allocations are modified to scope bound resource management
- Add some more units for encode apis for better coverage
- clang-formatted the code
- Improved the modularity for extending the tests to cover for
stride support for 420 input

Bug:
Test: ./libultrahdr_test

Change-Id: Iecc6242bca132229f51793132f0bc31cb04654f9