[VFABI] Add support for vector functions that return struct types (#119000)

This patch updates the `VFABIDemangler` to support vector functions that
return struct types. For example, a vector variant of `sincos` that
returns a vector of sine values and a vector of cosine values within a
struct.

This patch also adds some helpers for vectorizing types (including
struct types). Some of these are used in the `VFABIDemangler`, and
others will be used in subsequent patches, so this patch simply adds
tests for them.

0 files changed, 0 insertions, 0 deletions