[tests] Stablize tests for possible change in deref semantics

There's a potential change in dereferenceability attribute semantics in the nearish future.  See llvm-dev thread "RFC: Decomposing deref(N) into deref(N) + nofree" and D99100 for context.

This change simply adds appropriate attributes to tests to keep transform logic exercised under both old and new/proposed semantics.  Note that for many of these cases, O3 would infer exactly these attributes on the test IR.

This change handles the idiomatic pattern of a dereferenceable object being passed to a call which can not free that memory.  There's a couple other tests which need more one-off attention, they'll be handled in another change.