Test failures with ffmpeg 7.0

[lfos]

Running the test suite with 08d7f335 (Add compatibility with FFMPEG 7.0, 2024-05-08) and with ffmpeg 7.0, there seem to be several test failures:

The following tests FAILED:
	30 - Clip:verify parent Timeline (Failed)
	34 - Clip:time remapping (Failed)
	35 - Clip:resample_audio_8000_to_48000_reverse (Failed)
	92 - FrameMapper:resample_audio_48000_to_41000 (Failed)
	93 - FrameMapper:resample_audio_mapper (Failed)
	172 - Timeline:Multi-threaded Timeline Add/Remove Clip (Failed)

The failures themselves all look fairly similar and contain output such as

[SWR @ 0x7df3fcb2e380] Input channel layout "" is invalid or unsupported.
[SWR @ 0x7df3fcb2e380] Context has not been initialized

@eclipseo Any idea? Do you remember whether you manually ran the full test suite with ffmpeg 7.0 and with the final version of the changes proposed in PR #954?

It'd also be good to extend the GitHub workflows to run the build and full test suite with ffmpeg 7.0.