feat(PointCloud): increase range of picking to u32

[HoloTheDrunk]

Description

Change the picking IDs from u16 to u32.

Motivation and Context

Effectively eliminates the possibility of not having enough IDs to perform picking until GPUs start having 32GB+ of VRAM.
Tested on Firefox 123.0 (64-bit) on Ubuntu Linux 22.04.4 LTS x86_64

[HoloTheDrunk]

I don't know where the functional test errors are coming from, I can't replicate them locally so I'm guessing (hoping) it's a toolchain problem and not on my end

[Desplandis]

You encode each 48-bits unique_id value as 3 uint16. However, you read the resulting texture with a uint8 buffer (see c3dEngine#renderViewToBuffer)...

I don't think values are preserved here.

[HoloTheDrunk]

We can provide a u16 buffer ourselves

- const buffer = view.mainLoop.gfxEngine.renderViewToBuffer(
-     { camera: view.camera, scene: tileLayer.object3d },
-     {
-         x: viewCoords.x - radius,
-         y: viewCoords.y - radius,
-         width: 1 + radius * 2,
-         height: 1 + radius * 2,
-     });
+ const zone = {
+     x: viewCoords.x - radius,
+     y: viewCoords.y - radius,
+     width: 1 + radius * 2,
+     height: 1 + radius * 2,
+ };
+ zone.buffer = new Uint16Array(4 * zone.width * zone.height);
+ const buffer = view.mainLoop.gfxEngine.renderViewToBuffer(
+     { camera: view.camera, scene: tileLayer.object3d },
+     zone,
+ );

But looking into things a bit more I'm not sure how this is gonna interact with the default fullSizeRenderTarget used by the c3DEngine that gets created with u8 rgba formatting.
I currently don't have an example I could use to check for this issue, as the results don't change for the example I originally used for this PR (potree 3d map).