Implement specialization constant support in numthreads / local_size … #6935

Job	Run time
build (linux, debug, gcc, x86_64)	6m 16s
build (linux, release, gcc, x86_64)	6m 16s
build (linux, release, gcc, wasm)	6m 17s
build (macos, debug, clang, aarch64)	6m 16s
build (macos, release, clang, aarch64)	6m 17s
build (windows, debug, cl, x86_64)	6m 10s
build (windows, release, cl, x86_64)	6m 20s
build (linux, release, gcc, aarch64, smoke, false, self-hosted, Linux, ARM64, true)	6m 35s
	50m 27s

Provide feedback