Feature Request: make ability to add from 3rd party photo services more obvious

### What

When running a user testing session they wanted to add images from Google Photos to an existing Tiled Gallery block. They had already connected Google Photos when using another block so the connection was available.

However currently this option is very well hidden. There is:

- no option in the block's toolbar
- no option in the Inspector Controls
- no option (seemingly) in the Media Library

Example:

In reality the way you do this is to go to the top left corner of the Media Library and you can see the option but this is extremely well hidden:

When _creating_ the block this option is front and center so we need to bring the "edit" state into parity:

### Why

Customers want to bring in their photos. Many sites on WordPress.com have placeholder content including in Galleries. Therefore we need to ensure users can complete this action in a simple manner. Currently it's too hidden.

### How

Add options to the Media Library under "Add new".

Add an option to the Block Toolbar or Inspedtor Controls.

Start by tracing the Tiled Gallery block's edit state and the Media Library flow, focusing on the existing "Add new" entry and the Block Toolbar or Inspector Controls. Done means the Google Photos option is discoverable while editing an existing gallery and is consistent with the option shown when creating the block.

Written by the indexing model from the issue text.