merge_pr_48648

Support custom element reactions for moveBefore

• A new custom element reaction: connectedMoveCallback
• Called when the moved element is re-inserted
• Falls back to calling disconnectedMove/connectedMove if not provided.

Bug: 40150299
Change-Id: I0d3ed83ca03bbffcd2db79d1c421d8d155a4d9c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5920804
Reviewed-by: Dominic Farolino [email protected]
Commit-Queue: Noam Rosenthal [email protected]
Cr-Commit-Position: refs/heads/main@{#1369383}