refactor lwc:dom="manual" directive to act synchronously

[caridy]

Description

Today, lwc:dom="manual" relies on mutation observer to apply the right keys and css tokens for newly inserted nodes, but it happens on the next tick, causing some weird behavior, and unpredictable results.

Proposal

Patch DOM APIs on the portal elements so any manual operation on the node should automatically be picked up in a synch fashion, then, any new node inserted should automatically become a new portal element by transitivity, so they can pick deep insertion points as well.