fix: vendor and fix XRControllerModelFactory

[saitonakamura]

Following the discussion I vendored XRControllerModelFactory to react-xr along with some changes inside.

The main point of this is to fix problems with connecting/disconnecting different or same controllers, turns out webxr world is crazy full of quirks (who'd have thought). It all started in pmndrs/three-stdlib#214: there I tried to fix a problem when you connect and disconnect controllers and it doesn't unsubscribe from connected event. Thing is, in three, WebXRController are only created twice and never recreated, but they spew out connected/disconnected events. Connecting and disconnecting same or different controllers before this fix would result in ever more increasing connected event listeners each trying to load and add the scene. I've added the unsubscription fix, but it shot me in the foot in the most weird way. Turns out, SteamVR is connecting controllers in a peculiar way: it first dispatches inputsourceschange event with added: [some input source data], then immediately inputsourceschange with removed: [the input source that was just added] and then inputsourceschange with added: [proper input source]. And with the fix, it just unsubscribes from connected and never has a chance to resubscribe (cause it's kind of the same controller). With all that in mind I refactored XRControllerModelFactory, XRControllerModel and ControllerModel into somewhat cohesive picture that works with all this quirks. We tested it on multiple devies including Oculus Go, Quest 1, 2 and Pro, Rift S, Valve Index, Vive Cosmos and the others and we've yet to find more problems with it, this works robust. I don't really like the way it looks now, because logic is bit scattered all over the place, but it's no worse than it was before IMO

The other thing I did in this PR is to add a few events that XRControllerModel now dispatches, namely, modelconnected/disconnected and motionconnected/disconnected. They're not currently used in react-xr code, it's only used in our own app code to do 2 things:

1. Analyze data from MotionController to dispatch events such as button press/thumbstick move/etc. This is directly applicable to react-xr and I plan to expose it as an additional api surface to Interactive
2. Add more 3d stuff to the controller model, we add a tutorial that shows which button does what. Don't see a clear way for react-xr to take advantage of it right now, except for examples maybe

I'm willing to move these events dispatch to a separate PR if it's any problem

[saitonakamura]

Further plans concerning this:

1. Added button/thumbsticks events to the Interactive component
2. Try to port this fixes to three examples and then backport them to three-stdlib
3. Maybe also vendor HandModel and check if it works alright, haven't tested it much for now

[CodyJasonBennett]

Awesome, this has been a very fragile area for a long time. I'll merge and release this under v5.1.4 and follow-up with #238 under v5.2.0 which you can target in your app.