[popover2] fix(showContextMenu): close on backdrop click

[adidahiya]

Checklist

• Includes tests
• Update documentation

Changes proposed in this pull request:

Previously, a user-supplied onClose would override our handleClose callback which is responsible for closing the uncontrolled ContextMenu2Popover.

Now, our handleClose callback takes precedence. We still take care to call the user's onClose() callback if provided.

Reviewers should focus on:

context menus opened with showContextMenu({ onClose: () => {/* */} }) should close when clicking on the popover backdrop.

Screenshot

[adidahiya]

[popover2] fix(showContextMenu): close correctly when onClose is defined

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.

[adidahiya]

add unit test

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.