Framework: Deprecate uid in favor of clientId

[aduth]

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;
    }
} );

[youknowriad]

I personally prefer the concisness of uid even if clientId is more descriptive but noting that client can have several meanings :)

Anyway, I don't care too much and this PR is very hard to review/upgrade. I kind of trust our tests for it, so I'm approving to avoid staling PR. (I took a look but it's not easy to validate all the implications)

[gziolo]

[gziolo]

I also skimmed those changes. We have deprecations for both updated props in case of components and for updated selectors. We should still include some notes in the deprecation document.

[gziolo]

This is a really cool usage of createHigherOrderComponent 👍

[aduth]

Added a broad note to the deprecated.md document:

• All references to a block's uid have been replaced with equivalent props and selectors for clientId.

Rebased and did another pass of instances of uid in the codebase. End-to-end tests were uncooperative locally, but hoping Travis takes more kindly to them.