GStreamer imsdk camera test suite

[nitinn22]

This test suite provides comprehensive validation of camera functionality using GStreamer with Qualcomm's qtiqmmfsrc plugin (downstream) or libcamerasrc (upstream). Tests run in a specific sequence to validate different camera capabilities progressively.

The test suite automatically detects which camera source plugin is available:

1. qtiqmmfsrc (Qualcomm CAMX downstream): Runs 10 tests

   • Fakesink (2) + Preview (2) + Encode (6)
   • Priority: Used by default when both plugins are detected
   • Supports NV12 and UBWC formats

2. libcamerasrc (upstream): Runs 7 tests

   • Fakesink (1) + Preview (3) + Encode (3)
   • Used when qtiqmmfsrc is not available or explicitly requested
   • Supports NV12 format only

[smuppand]

This PR would be much easier to review and maintain if it is reduced to the minimum supported feature set.

Right now the suite is over-expanded for an initial submission: the runner is very large, the README is very long, and the shared library change includes helper additions that do not appear to be required by the suite’s current execution path.

Please tighten this PR. Suggested cleanup:

1. Remove interfaces that are not actually implemented end-to-end yet

   • e.g. --test-name / CAMERA_TEST_NAME if single-test filtering is not wired up
   • remove snapshot-related helper additions if snapshot tests are not actually executed

2. Keep only shared lib_gstreamer.sh helpers that are used by this suite today

3. Reduce the README to the essentials

   • overview
   • prerequisites
   • actual supported test matrix
   • parameters
   • basic troubleshooting

4. Split into 2 commits

   • shared helper additions
   • Camera_Tests suite files

5. Fix the YAML wrapper to the repo-standard form while respinning

If needed, it would also be reasonable to reduce this to a smaller MVP first (for example only the verified backend/test paths), and then add more coverage in follow-up PRs.