Revert mipmap generation on render targets from 66a7657

[MajorPainTheCactus]

Summary

• Reverts the render target mipmap generation feature from 66a7657 (fix mipmaps on generated textures) across D3D10, D3D11, and D3D12
• Removes GENERATE_MIPS / MipLevels = 0 on shader pass render targets and the associated GenerateMips / d3d12_generate_mipmaps calls after render passes
• Preserves the non-square texture mipmap count fix (|| vs && loop condition) which is a valid standalone bugfix
• Preserves all D3D12 HDR pipeline fixes from 7df941e (blend pipelines, resource state management, overlay support, etc.)

Context

The mipmap changes from 66a7657 were previously reverted in 226d7b1 (D3D12 only) and then partially re-merged in 7df941e alongside HDR pipeline fixes. This PR cleanly separates the two, reverting only the mipmap render target feature while keeping the HDR fixes intact.

[MajorPainTheCactus]

Hi @hizzlekizzle this PR contains all the mip map generation changes reverted so that we can fix up the issues the original commit 66a7657 introduced. We can just work on that commit in a local branch to add support for tagging specific passes/render targets for mip map generation rather than this more blanket change.

It should be noted I've kept an actual valid fix from 66a7657:

while ((width > 1) || (height > 1))

to stop validation errors