[compiler-rt] Fix interception_win.cpp arm64 instruction lengths

Updates GetInstructionSize to account for arm64 instruction sizes.

ARM64 instruction are always 4 bytes long but GetInstructionSize in
interception_win.cpp assumes x86_64 which has mixed sizes.

Fix is for: https://github.com/llvm/llvm-project/issues/64319

Before the changeclang_rt.asan_dynamic-aarch64.dll would crash at:
OverrideFunction -> OverrideFunctionWithHotPatch -> GetInstructionSize:825

After the change:
dllthunkintercept -> dllthunkgetrealaddressordie -> InternalGetProcAddress