[video_player] add support for content-uri based videos (android only)

[byunme]

Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.

This PR adds playback from contentUri support for the video_player plugin (Android only).

The current Android implementation uses ExoPlayer, which already supports playback from uri, so this change is just to surface contentUri as a valid video datasource on the dart side.

List which issues are fixed by this PR. You must list at least one issue.
flutter/flutter#88130

If you had to change anything in the flutter/tests repo, include a link to the migration guide as per the breaking change policy.

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. (Note that unlike the flutter/flutter repo, the flutter/plugins repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the plugin 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.
• I updated CHANGELOG.md to add a description of the change.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test exempt.
• All existing and new tests are passing.

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[stuartmorgan-g]

Nit: a new feature should bump the minor version rather than the patch.

[stuartmorgan-g]

Thanks for the submission!

@blasten This looks pretty straightforward; can you take a look?

[blasten]

don't forget to delete

[stuartmorgan-g]

It'll be removed once the PR is split (https://github.com/flutter/flutter/wiki/Contributing-to-Plugins-and-Packages#changing-federated-plugins). It can't accidentally be left because this fails publishable.

[stuartmorgan-g]

@byunme Are you planning on splitting this into the component PRs now so that we can move forward with landing this?

[byunme]

@stuartmorgan Sorry for the delay, I've split off the interface part here: #4307

[jmagman]

This needs to be merged ASAP to unblock the framework tree. #4307

I don't have permissions to push to this branch, taking it to #4330

[jmagman]

Obsolesced by #4330.

Thanks for the contribution, @byunme, sorry I had to split the PR out to reopen the submit queues ASAP.