Add option to force generic algorithms on x86 (microsoft#22917)

Option is named onnxruntime_FORCE_GENERIC_ALGORITHMS

Follow up to microsoft#22125.

### Description
This change adds compile-time option to disable optimized algorithms and
use generic algorithms (exclude AVX* and SSE etc in GEMM) on x86. This
new option is intended only for testing these algorithms, not for
production use.

Following build command on linux x86_64 builds onnxruntime with new
option enabled:
`./build.sh --parallel --cmake_extra_defines
onnxruntime_FORCE_GENERIC_ALGORITHMS=1`

### Motivation and Context
This change allows testing generic algorithms. This may be needed for
platforms which don't have optimized implementations available, like in
microsoft#22125.

onnxruntime/core/mlas/lib/qgemm.h

@@ -867,6 +867,7 @@ MlasGemmQuantGetDispatch(
 {
     const MLAS_GEMM_QUANT_DISPATCH* GemmQuantDispatch = &MlasGemmQuantDispatchDefault;
 
+#if !defined(FORCE_GENERIC_ALGORITHMS)
 #if defined(MLAS_TARGET_AMD64_IX86)
     if (AIsSigned) {
         GemmQuantDispatch =