fix: hot-reload broken VCam apply retry

[pravusjif]

WHY

I encountered these 3 bugs that affect creators dev-exp + unity devs dev-exp:

1. [Cannot reproduce anymore...] Since recently, during the hot-reload of a local scene, Unity may crash randomly while the scene reloads.
2. [Cannot reproduce anymore...] Since recently, during hot-reload of a local scene, Unity may end up throwing ObjectDisposedException infinitely
3. I detected that if a scene uses a VCam from the beginning, it works OK the first load but after hot-reloading many many times the VCam is never re-assigned correctly at the beginning of the scene.

Virtual Camera breaking after hot-reload (3.) demo (second 0:11)

Screen.Recording.2025-06-02.at.1.24.20.PM.mp4

WHAT

1. Fixed Unity Editor crash when hot-reloading a scene by placing the Resources.UnloadUnusedAssets(); call during LSD to be called AFTER we waited for the scene to reload. I guess that maybe some unused assets may be getting re-used during the WaitUntilNewSceneIsFullyLoadedAsync() and that may be why it exploded there.
   • Commit: 7ddd61f
2. Fixed the ObjectDisposedException infinite throwing observed during hot-reload by adding a check to know if the token is able to be Cancelled.
   • Commit: 04cd711
3. Fixed the Virtual Camera application being broken after hot-reload on scenes that use the VCam since the beginning, by making sure that the MainCameraSystem retries when the target CRDT Entity didn't have the PBVirtualCamera component yet.
   • Commit: 3198445

TEST INTSTRUCTIONS

1. Download this test scene
2. Enter the scene root folder and run npm i and then npm run start -- --explorer-alpha
3. Close the Explorer that auto-opened. Leave the scene running in the console/terminal.
4. Download the build from this PR and connect it to the running scene using the console command according to your OS
5. Once the scene loads, confirm that the camera of that scene is a TOP DOWN camera (not any of the normal character cameras)
6. Leave the Explorer running and in any text editor open index.ts file of the scene that you have running (ideally in a different monitor)
7. Modify the const CHANGE_THIS_VALUE_FOR_HOT_RELOAD = 1 (that's in the index.ts file) value to any different number to trigger a hot-reload of the scene in the Explorer -> Confirm that the scene has been automatically reloaded (hot-reload) and that the Camera is again put as a TOP DOWN camera.
8. Repeat step 7 for another 9 times to confirm that the virtual camera always works as expected after a hot-reload.

[github-actions]

Windows and Mac build successful in Unity Cloud! You can find a link to the downloadable artifact below.

Name	Link
Commit	1a5f4e5
Logs	https://github.com/decentraland/unity-explorer/actions/runs/15454940465
Download Windows	https://github.com/decentraland/unity-explorer/suites/39635075791/artifacts/3263712927
Download Windows S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/fix/2-exceptions-1-vcam/pr-10028-1a5f4e5/Decentraland_windows64.zip
Download Mac	https://github.com/decentraland/unity-explorer/suites/39635075791/artifacts/3263672335
Download Mac S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/fix/2-exceptions-1-vcam/pr-10028-1a5f4e5/Decentraland_macos.zip
Built on	2025-06-05T00:12:43Z

[DafGreco]

✔️ PR reviewed and approved by QA on both platforms following instructions playing both happy and un-happy path

Regressions for this ticket had been performed in order to verify that the normal flow is working as expected:

• [✔️ ] Backpack and wearables in world
• [✔️] Emotes in world and in backpack
• [✔️ ] Teleport with map/coordinates/Jump In
• [✔️ ] Profile card
• [✔️ ] Camera
• [ ✔️] Skybox
• [✔️ ] Settings