Missing support for SPV_INTEL_inline_assembly extension

[jdnk]

OpAsmINTEL and OpAsmTargetINTEL instructions from SPV_INTEL_inline_assembly should be allowed in the same section as type declarations. This is currently not allowed in SPIRV-Tools which triggers an error during validation.

Reproducible example (using LLVM 19):

// foo.c
void foo (const float * restrict a, const float * restrict b, float * restrict c) {
    __asm__ ("nop");
}

> clang -S -emit-llvm foo.c -o foo.ll
> llc -O3 -mtriple=spirv64-unknown-unknown --spirv-ext=+SPV_INTEL_inline_assembly foo.ll -o foo.spt
> spirv-as foo.spt -o foo.spv
> spirv-val foo.spv
error: line 24: AsmTargetINTEL must appear in a block
  %12 = OpAsmTargetINTEL "spirv64-unknown-unknown"

Note that the spirv-as line works only with fixed headers.

When trying to link the module containing inline assembly, spirv-link complains with a similar error:

> spirv-link foo.spv foo.spv -o foo_linked.spv
error: 0: Unhandled inst type (opcode: 5609) found outside function definition.
error: 0: Failed to build module 1 out of 1.

@mmerecki FYI