Now that we have video messages working end-to-end, we can "flip the switch" to enable video messages.

Specifically:

1. Set serverCanHandle to true for video types in lib/media/file-utils
2. Set versionCode for hasMinCodeVersion check in multimedia-message-spec to 158.
3. Add MediaLibrary.MediaType.video to mediaType array in multimedia-gallery-keyboard so users can select videos from their media gallery.
4. Set persistConfig.version to 32 so multimedia unshimming migration runs.
5. Add messageTypes.MULTIMEDIA to unshim-utils:localUnshimTypes

All the diffs that came before this one tested various parts of the video message ssytem independently.

In addition I've done a decent amount of testing in my local dev environment to make sure things work as expected... going to do additional testing before I land this diff... and further testing before making a release that includes these changes.