fix: limit raycast queries per frame

[oOZakMcKrackeNOo]

What?

In order to prevent casting many raycasts on the same frame, one possible solution is to make query messages replace older ones each time they arrive to the client. But this approach leads to another problem: sometimes we need to be able to cast more than one ray per frame (i.e. a car that needs to cast three rays on the front to avoid colliding). To allow this, Raycast Instances come to the rescue: a raycast instance is a numeric id that identifies each query that we need to make each frame.

Why?

When casting raycasts continuously on each update iteration, several messages can accumulate in client messaging bus. This can lead to performance and user experience issues because raycasts may be calculated many times each frame when not needed. Also, other messages processing are contingent on how many queries are enqueued on the same bus, aggravating the issue.

[moliva]

How about this notation instead?

  hitFirst(ray: Ray, hitCallback: (event: RaycastHitEntity) => void, id?: number): void
  hitAll(ray: Ray, hitCallback: (event: RaycastHitEntities) => void, id?: number): void
  /** @internal */
  hitFirstAvatar(ray: Ray, hitCallback: (event: RaycastHitAvatar) => void): void
  /** @internal */
  hitAllAvatars(ray: Ray, hitCallback: (event: RaycastHitAvatars) => void): void
}```

[moliva]

Could we take the 'rqhf' and 'rqha' to a QueryType prefix enum?

[BrianAmadori]

Already requested this change in unity-client. But I'm repeating here:
in encodeSceneMessage under dcl.ts we could pre-pack the sceneId+tag in the tag field, avoiding the expensive StringBuilder call in unity side.

[moliva]

Do we need to export this enum? If not needed, let's drop the export.