Related: #7669

This pull request seeks to deprecate all references to "UID" in the codebase with equivalent "Client ID" naming. This change is being made in an effort to promote consistency on abbreviation capitalization, where, for example, previous selectors...

• getAdjacentBlockUid
• getBlockRootUID

...become:

• getAdjacentBlockClientId
• getBlockRootClientId

Observing the changes, you should see a number of other inconsistencies having been addressed here, including references to a block's id where uid is intended.

Note: This is a massive pull request, which is prone to becoming stale very quickly. I'd urge that this be acted upon soon to avoid issues with merge conflicts.

Implementation notes:

This does include deprecations, not only for the selectors, but also covering components which we expose on wp.editor which accept some prop referencing a "uid". This is achieved through a new (and temporary) withDeprecatedUniqueId higher-order component.

Testing instructions:

Ensure all forms of automated tests pass.

Verify there are no lingering references to UID in the entire codebase, aside from those necessary for temporary compatibility until total removal.

Ensure that deprecations work effectively. Here's a test block as an example, whose edit function depends on both the id prop being passed and the BlockTitle component accepting a uid prop:

wp.blocks.registerBlockType( 'aduth/test-uid', {
	title: 'Test UID Block',

    category: 'common',
    
    edit: function( props ) {
        return wp.element.createElement( wp.editor.BlockTitle, { uid: props.id } );
    },
    
    save: function() {
        return null;
    }
} );