Implement the actual Gutenberg Story block on WPAndroid

[mzorz]

Currently, we're producing the Gutenberg block structure by hardcoding tags and using Gson serialization. We'll want to actually use mobile gutenberg to:

• integrate the editor flows (show the block's placeholder, implement navigation to the Story editor) edit see Editing from local serialized Story #445
• be able to correctly validate and save block information at creation time. This we might mark as optional?, we'll dig into this when the time comes - I'm thinking we probably can still leave this part as is, given in WPAndroid we're already using matchers in the BlockProcessor structure for dealing with block updates with media information coming from the server.

[mzorz]

Some notes
wordpress-mobile/gutenberg-mobile#854 (comment)

To do this on Mobile, we might have to import the JetPack block, right?

I think we just need to read the VideoPress hash, query the native side (there is an API call that from a VP hash does return video info) and replace it with the video URL when the call returns.

Related Automattic/jetpack#12358

[mzorz]

Feature branch PR being worked on here wordpress-mobile/WordPress-Android#13130

[mzorz]

This is completed 🎉