[OMPIRBuilder] Replace getAllocatedType with getAllocationSize (#181844)
Replace size queries using getTypeStoreSize(getAllocatedType()) with
getAllocationSize(DL) in createTaskloop, createTask, emitTargetTask, and
emitTargetTaskProxyFunction. For GEP type arguments in
emitNonContiguousDescriptor and emitOffloadingArrays, use the local
ArrayTy/PointerArrayType variables already in scope instead of
re-querying the alloca.
The store size of a struct is the same as the allocation size, so this
part should be NFC, and removes unnecessary uses of getAllocatedType, in
pursuit of the eventual deprecation of the getAllocatedType interface.
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>