Feat: tooltip anchor can be set with element instance as well as id

[scomea]

The anchor element used by tooltip can currently only be set via an anchor reference. This is limiting particularly in cross shadow dom scenarios. This change exposes anchorElement as a public api where developers can set the tooltip anchor programmatically by passing an element instance.

🎫 Issues

ad hoc

📑 Test Plan

Added a basic swapping test

✅ Checklist

General

• I have included a change request file using $ yarn change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

Component-specific

• I have added a new component
• I have modified an existing component
• I have updated the definition file
• I have updated the configuration file

[radium-v]

This approach seems duplicative. In this test, the anchor's ID is already known, so what benefit does setting the anchorElement provide over setting the anchor property directly?

[scomea]

The point of the feature is to allow setting the anchor via an element instance, in the current implementation only an id works. The main benefit of setting the anchor element directly is that it enables tooltips to be anchored to elements in shadow trees which can't be rereferred to via id. As I write this I'm realizing I'd need to swap describedby/labelledby for description/label in that instance as well, rethinking...