MISC: Add support for frame2d.image_rgba()

[torbsorb]

We have samples which utilize the new feature where you can directly copy in BGR format. To keep samples aligned we add the missing feature here.

test_release.py does not require explicit testing with image_bgra().

pytest has been run with and without the marker physical_camera. The test was run on Windows, and the samples tests failed because of something unrelated (not root caused, but points towards pytest.helpers.run_sample). All samples were tested directly without pytest. They all pass.

Note! We should also consider adding BGR for pointCloud.

MISC

[eskaur]

Regarding the commit-message:

• I don't think it's necessary to mention that some tests failed locally, etc. It's kind of a pre-requisite that the CI passes and that the added functionality works.
• I don't think you should mention test_release.py because that file doesn't exist in this repo.

[eskaur]

Looks good. Feel free to rebase on master whenever.