Pin dxmt at the BC texture and memory fixes

[spitefulowl]

Depends on willfaust/dxmt#16 (see Merge order).

Change

This moves the dxmt submodule to the head of willfaust/dxmt#16. That PR fixes three problems on GPUs without BC texture support:

• the purple lighting, black ground and black scope lens in Metro 2033 Redux;
• jetsam kills during loads in Metro 2033 Redux and Hollow Knight;
• the lack of frame-time logging that would show what a slow scene waits on.

Its six commits:

• dxmt: log GPU busy time, readback waits and draws every 64 frames
• dxmt: zero blit commands; zero-fill remapped BC textures physically
• d3d11: refill mip levels that a mipClampBC copy left empty
• dxmt: zero-fill the whole grown zero buffer
• d3d11: wait for the GPU instead of renaming staging past a budget
• dxmt: flush resource initializer uploads every 64 MB

Device results and the new DXMT options (d3d11.asyncRefill, d3d11.stagingRenameBudgetMB) are described in willfaust/dxmt#16. The config catalog does not change, because these commits add DXMT options but no environment switch.

Rebased onto main. willfaust/dxmt#16 is rebased onto the dxmt commit main pins now (020a848) and pinned at e874a1556fb. Its former commit that dropped each shader's parsed DXBC is gone: upstream dxmt#6 does that in airconv.

Merge order

The pin points at the head commit of willfaust/dxmt#16, which so far exists only in the spitefulowl fork. Merge that one first.

• If it is merged with a merge commit, the pinned commit is then in willfaust/dxmt unchanged, and this PR can follow as is.
• If it is squashed or rebased, I will move the pin to the resulting commit before this one is merged.

Rebuild (no binaries in this PR)

• arm64ec-windows/d3d11.dll (DXMT PE meson build)
• the i386 DXMT DLLs (build/wine-i386/build.sh)
• app/Madeira/libdxmt_combined.a (full build/dxmt-ios/build.sh)

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