[Materializer] Remove wrong SetSizeAndAlignmentFromType().

This function is unused.  It's also wrong, because it computes
the size and the alignment of the type without asking the runtime,
so it doesn't work for any language that has one (e.g. swift).

One could consider re-implementing this passing an execution scope
context, and modifying GetTypeBitAlign() to do the right thing,
but given there are no uses, it's not really useful.

llvm-svn: 368249