fix: throttle tree generation when the player teleports

[lorux0]

What does this PR change?

Fixes #7150

A fix has been introduced here: #6643 to regenerate the terrain props whenever the user moves between realms. That is OK, however the process is very expensive due more than 100k iterations (depending on how many trees and props).

The changes introduces a throttling over frames to re-generate the trees (1000 trees every frame).

Test Instructions

Follow steps from this issue: #5873

1. Go to any empty parcel
2. Go to a world
3. Go back to any empty parcel
4. Go to any scene
5. Check that you dont see trees overlapping the scenes nor worlds
6. The load times will be higher, check that takes a reasonable duration

Quality Checklist

• Changes have been tested locally
• Documentation has been updated (if required)
• Performance impact has been considered
• For SDK features: Test scene is included

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