[SPIR-V] Improve type inference: deduce types of composite data structures (#86782)

This PR improves type inference in general and deduces types of
composite data structures in particular. Also added a way to insert a
bitcast to make a fun call valid in case of arguments types mismatch due
to opaque pointers type inference.

The attached test `pointers/nested-struct-opaque-pointers.ll`
demonstrates new capabilities: the SPIRV code emitted for this test is
now (1) valid in a sense of data field types and (2) accepted by
`spirv-val`.

More strict LIT checks, support of more composite data structures and
improvement of fun calls from the perspective of type correctness are
main todo's at the moment.