fix: have icons use the new render management system

[BeksOmega]

The basics

• I branched from develop
• My pull request is against develop
• My code follows the style guide
• I ran npm run format and npm run lint

The details

Resolves

Work on #7068

Proposed Changes

1. Adds a new method to the render management system to immediately trigger any queued renders. This should only be used in cases where it's necessary for backwards compatibility (like this one).
2. Switches icon methods over to use the render management system (with the immediate trigger).
3. Adds dummy promises to the return value of all setBubbleVisible methods.

Reason for Changes

1. We need adding icons to trigger a render immediately so that if the bubbles are set to be visible immediately, they are positioned correctly. Eventually we want to move this to be promises-based (so setting the visibility will wait for any queued renders to finish first). But that is a breaking change.
2. This gets us one step closer to tearing out the old render management system.
3. This makes it easier for external devs to transition to the new promises based system.

Test Coverage

All tests pass! Also quickly tested block.setCommentText('test'); block.getIcon('comment').setBubbleVisible(true); in the browser console to reassure myself that it was indeed working.

[cpcallen]

Make sure that this PR still has a deprecation tag once it's been submitted: one of the bots seems to like to try to remove that tag.

Not for this PR, but: given similarity of code have you considered introducing a BubbleIcon intermediate class between Icon and Comment/Mutator/WarningIcon?

[BeksOmega]

Maribeth actually requested on the next pull request that I remove the dummy promises, and we just cleanly break people later. So I've reverted that change and removed the deprecation notice!

[Edit: Wrt the BubbleIcon I had not considered doing that, but may be worth investigating!]