Bump FFmpeg to 7.0

[SurfaceS]

We are currently running on FFmpeg 6.1.

April 5th, 2024, FFmpeg 7.0 "Dijkstra"

A new major release, FFmpeg 7.0 "Dijkstra", is now available for download. The most noteworthy changes for most users are a native VVC decoder (currently experimental, until more fuzzing is done), IAMF support, or a multi-threaded ffmpeg CLI tool.

This release is not backwards compatible, removing APIs deprecated before 6.0. The biggest change for most library callers will be the removal of the old bitmask-based channel layout API, replaced by the AVChannelLayout API allowing such features as custom channel ordering, or Ambisonics. Certain deprecated ffmpeg CLI options were also removed, and a C11-compliant compiler is now required to build the code.

As usual, there is also a number of new supported formats and codecs, new filters, APIs, and countless smaller features and bugfixes. Compared to 6.1, the git repository contains almost ∼2000 new commits by ∼100 authors, touching >100000 lines in ∼2000 files — thanks to everyone who contributed. See the Changelog, APIchanges, and the git log for more comprehensive lists of changes.