[PATCH 69/79] [Backport to 15] Backport spirv-preserve-auxdata changes (#2180)

[PATCH 69/79] [Backport to 15] Backport spirv-preserve-auxdata changes (#2180)

Backport the below changes to 15:

f729c49
89d658c
9823690
d498f48
d24b9c6

I made the following changes that are not in the original changes:

Use llvm::Optional instead of std::optional
Port tests to not use opaque pointers and related flags
Fix patch fail due to missing unrelated function in this branch

Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>
Gbp-Pq: Name 0069-Backport-to-15-Backport-spirv-preserve-auxdata-chang.patch