support in-element & wormhole

[patricklx]

this injects a InElement component into the component tree, which has its bounds set to the target. it also adds it as a root tree element, so the click & hover work correctly.
This is also done for EmberWormhole, the code checks for the EmberWormhole instance and changes the bounds to its target element

resolves #1255
closes #1375

[patricklx]

@RobbieTheWagner this is ready for review

[RobbieTheWagner]

This seems okay to me, I just wonder if there is anything built in to the internals of glimmer or modifiers that could make this easier? @wycats @chancancode @MelSumner @kategengler who is working on things related to this? Would love to get a thumbs up from them that this is the best way to do things.

[NullVoxPopuli]

lgtm, though, I'd like to see it tested out first -- got a demo / gif or something of before/after?

[patricklx]

lgtm, though, I'd like to see it tested out first -- got a demo / gif or something of before/after?

Not at the moment, in holidays...
There are tests for it. Or you can download the artifact and test it :)

[RobbieTheWagner]

@NullVoxPopuli I am sure this is functionally fine, I just wanted to make sure there wasn't an easier glimmer API we could hook into or something because this all seems very manual.

[RobbieTheWagner]

Since there has been no response from stakeholders, I am going to merge this. If there is a better way, we can always update things later. Thanks for the PR @patricklx!