[camerax] Implement video capture for CameraX android camera re-write (remake to fix cla issue)

[gmackall]

This is a re-creation of this older PR. Somehow, git stash became an author of a commit on the old pr, which was then parsed as an actual person, and that actual person has not signed the CLA. Rebasing the 60+ commits on top of that old commit to amend the author was prohibitively hard, and so I've squashed the old commits into a new branch (if any git experts are aware of an easier fix for this please let me know!).

Old pr description:
This PR implements video capture for the CameraX re-write of the android camera plugin.

flutter/flutter#111138

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/packages repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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[gmackall]

Closing this as we pushed this resolved git history to the original branch, updating the original PR.

git push --force-with-lease origin video_cla_fix:video_capture