Fix massive validation errors when enabling TAA + MSAA

[darksylinc]

TAA + MSAA would make Godot request unnecessary flags for an MSAA velocity texture, flags that were not even actually needed.

This was causing:

1. Unsupported GPUs to fail completely (e.g. Intel Arc 770)
2. Wrong codepaths to be followed (causing validation errors, possibly crashes or glitches)
3. Unnecessary performance impact in all GPUs.

See
#71929 (comment)

[Calinou]

• Related to Add FidelityFX Super Resolution 2.2 (FSR 2.2.1) support. #81197 and Unexpectedly low performance of temporal antialiasing due to high GPU cost #61905.

cc @DarioSamo

[darksylinc]

Note: This only affects (performance & bugs) when both TAA & MSAA are enabled at the same time. This does not affect any issues that arise when TAA is enabled but MSAA is disabled.

[DarioSamo]

Yeah I've been talking with Matias and it was fairly suspect that the MSAA texture requested these attributes. Nothing that uses it afterwards will request it as the MSAA texture will resolve to the version of the texture that has storage and is the version of the texture used in TAA and FSR2.

[Calinou]

Tested locally (rebased on top of master ee15a2e35), it works as expected.

Performance comparison on https://github.com/Calinou/godot-reflection in 3840×2160 on a GeForce RTX 4090:

Antialiasing	Before	After (this PR)
TAA, no MSAA	271 FPS (3.69 mspf)	269 FPS (3.72 mspf)
TAA, 2× MSAA	236 FPS (4.24 mspf)	249 FPS (4.02 mspf)
TAA, 4× MSAA	206 FPS (4.85 mspf)	226 FPS (4.42 mspf)
TAA, 8× MSAA	171 FPS (5.85 mspf)	182 FPS (5.49 mspf)

Using MSAA with TAA still makes a positive visual difference by making moving edges less aliased, so it's still functional.

[akien-mga]

Thanks!

[YuriSizov]

Cherry-picked for 4.1.3.