Add video modality input support

[mohami2000]

Added support for video inputs in the sdk and tests. I also tested this with a real api key and it worked great!
The changes on modelproxy side are already merged to support this.

I tested inputting videos and it worked!

design doc
BUG=b/496208368

[s-alexey]

Changes look good. However, they conflict significantly with #12. We should decide on the merge order.

[mohami2000]

Changes look good. However, they conflict significantly with #12. We should decide on the merge order.

I think we should submit this first because it is needed to unblock some 1P partners :)

[dolaameng]

Thanks for adding this feature! LGTM. Will approve after we settle the user communication.

Also will wait for @s-alexey to take a final look with the refactoring code.

[mohami2000]

Thanks for adding this feature! LGTM. Will approve after we settle the user communication.

Also will wait for @s-alexey to take a final look with the refactoring code.

Synced offline

[dolaameng]

Approve to unblock users requests. Please follow up on the plans to extend this. Thanks for adding the feature!