ntdll, kernelbase: Stabilize RDR2 Social Club CEF on ARM64

[utkarshdalal]

Problem\n\nOn the ARM64EC Android build, Rockstar Social Club's CEF browser has two deterministic failures:\n\n1. The renderer aborts when V8 cannot reserve its 128 GiB sandbox after Wine has fragmented the 39-bit address space.\n2. After that is avoided, CEF's GPU path aborts in Skia because the backend format is invalid.\n\n## Change\n\n- For RDR2 (Steam app 1174180) on ARM64, reserve 0x2000000000-0x4000000000 during ntdll preload and register it as a Wine reserved area. VirtualAlloc2 can then replace that reservation when V8 creates its sandbox.\n- Append disable-gpu, disable-gpu-compositing, and disable-gpu-rasterization to every SocialClubHelper child process for RDR2.\n\nThe changes are scoped to Steam app 1174180 and do not modify Rockstar files or authentication.\n\n## Local validation\n\nEquivalent preload and in-process command-line shims were tested on the RP6:\n\n- V8's EXCEPTION_BREAKPOINT at libcef + 0xB4AEA0 is eliminated.\n- The Skia invalid-backend-format fatal is eliminated.\n- The renderer remains alive and Rockstar's offline sign-in page renders.\n\nThe remaining failure to load the online sign-in page is a separate CEF page-load issue and is being investigated independently.\n\n## Validation\n\n- git diff --check\n- GitHub ARM64EC and x86_64 build matrices