Editor: Rename all the hooks moved from blocks to editor

[gziolo]

Description

We recently moved almost all components from blocks module to `editor module. We didn't update the names of all filters and it looks like we should do it for consistency and easier discoverability.

This PR fixes it by renaming the following filters and expanding documentation:

• blocks.Autocomplete.completers -> editor.Autocomplete.completers
• blocks.BlockEdit -> editor.BlockEdit
• blocks.BlockListBlock -> editor.BlockListBlock
• blocks.MediaUpload -> editor.MediaUpload

TODO

• Forwarding and deprecation warnings when someone is using old hooks
• Update deprecation changelog

How has this been tested?

I made sure that:

• you are able to use advanced controls for all blocks (custom class name or anchor)
• blocks that use align feature are still properly aligned in the editor
• it is still possible to upload media using the library
• slash autocompleter still works

To test deprecations and doc changes at once. Paste the following snippet which got updated to use old hook:

var el = wp.element.createElement;

var withInspectorControls = wp.element.createHigherOrderComponent( function( BlockEdit ) {
	return function( props ) {
		return el(
			wp.element.Fragment,
			{},
			el(
				BlockEdit,
				props
			),
			el(
				wp.editor.InspectorControls,
				{},
				el(
					wp.components.PanelBody,
					{},
					'My custom control'
				)
			)
		);
	};
}, 'withInspectorControls' );

wp.hooks.addFilter( 'blocks.BlockEdit', 'my-plugin/with-inspector-controls', withInspectorControls );

Made sure it still works and deprecation message appears on the JS console:

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.

[youknowriad]

LGTM 👍