XeSS XMX on Linux (Proton) for Intel Arc: Xe-HPG, Xe2, Xe3

Real Intel XeSS super resolution and XeSS frame generation inside Proton games, running on the GPU’s XMX (matrix) units instead of the DP4a fallback that stock Wine/Proton gets. No Windows driver, no change to Proton or vkd3d-proton:

• igdext64.dll, a shim built on Intel’s open source dxvk-igdext, answers XeSS’ driver queries like an Intel driver and hands every C-for-Metal (CM) kernel XeSS submits over as a placeholder;
• a patched Mesa ANV Vulkan driver compiles those kernels with Intel’s compiler (IGC) on first use and runs them in place of the placeholders, inside the normal vkd3d-proton queue;
• ControlLib.dll, a stand-in for Intel’s Control Library, gives XeSS frame generation the override that Intel Graphics Software sets on Windows: XESS_FG=<n> in a game’s launch options;
• amd_fidelityfx_upscaler_dx12.dll and amd_fidelityfx_framegeneration_dx12.dll run a game’s FSR 3.1+ upscaling and frame generation on XeSS, so a game without XeSS gets XeSS on XMX and multi-frame generation as well: FSR=xess in its launch options…