fix(popover): size property now works when providing only event

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue Number: resolves #23528

What is the new behavior?

• the animations (incorrectly) assume that only the trigger prop would be used to determine popover dimensions when size="cover". However, the trigger could also be found via event.target if event is provided.
• I updated the animation code to pass in either the trigger element or the event target if no trigger was found and an event was provided.

Does this introduce a breaking change?

• Yes
• No

Other information