[mlir][spirv] Use larger range for target environment lookup function

[antiagainst]

Summary

Previously we only look at the directly passed-in op for a potential
spv.target_env attribute. This commit switches to use a larger range
and recursively check enclosing symbol tables.

Depends On D75868

[denis13]

mlir/docs/Dialects/SPIR-V.md

936

Do you mean handy here?

[mravishankar]

mlir/lib/Dialect/SPIRV/TargetAndABI.cpp

298

Nit: make this a while loop?

[antiagainst]

Address comments

[antiagainst]

mlir/docs/Dialects/SPIR-V.md

936

Oops, yes, good catch!