Tests don't support MSVC arm or arm64 architectures

There's several assumptions that MSVC or Win32 implies SSE support, e.g. https://github.com/KhronosGroup/OpenCL-CTS/blob/master/test_common/harness/conversions.cpp#L23, and there's detection for arm architectures and inline assembly using GCC/Clang syntax, e.g. https://github.com/KhronosGroup/OpenCL-CTS/blob/master/test_common/harness/rounding_mode.cpp#L25.

This needs some cleanup to use appropriate guards/gating that either incorporates MSVC-specific defines, or works across compilers.

Start with the architecture and compiler guards in test_common/harness/conversions.cpp and test_common/harness/rounding_mode.cpp, including the referenced lines. Trace how MSVC, Win32, ARM, and ARM64 are detected, then verify that the relevant tests build and run correctly for MSVC ARM and ARM64 without relying on unsupported assembly syntax or SSE assumptions.

Written by the indexing model from the issue text.