Use transient multisampled textures for `NormalPrepass` and `MotionVectorPrepass`

## What problem does this solve or what need does it fill?

Currently if MSAA enables, normal prepass and motion vector prepass are stored in multisampled textures, which wastes many VRAM and bandwidth. And sampling multisampled prepass textures isn't useful as we generally pass 0 as `sample_index` otherwise per-sample fragment shader is less efficient. Using resolved normal and motion vector textures doesn't need `sample_index` and they are anti-aliased.

For desktop that transient attachment doesn't save memory, this uses more VRAM for the unsampled textures.

## What solution would you like?

If MSAA enabled, use transient multisampled textures for `NormalPrepass` and `MotionVectorPrepass` and resolve them to unsampled textures.

## What alternative(s) have you considered?

Alternatively we can choose to always disable multisampling for `NormalPrepass` and `MotionVectorPrepass` as them usually have less visual impact.

## Additional context

Transient attachment is added in wgpu v28 and it is more efficient on TBDR and usually can't save VRAM on desktop.

Start by locating the NormalPrepass and MotionVectorPrepass render entry points and tracing how their MSAA attachments are created. Done means that, when MSAA is enabled, transient multisampled attachments resolve to unsampled normal and motion-vector textures without requiring a sample index, while the desktop trade-off is preserved.

Written by the indexing model from the issue text.