[LowerConstantIntrinsics] Improve tests related to llvm.objectsize. NFC (#132364)
Adding some new test cases (including FIXME:s) to highlight some bugs
related to lowering of llvm.objectsize.
One special case is when there are getelementptr instruction with index
types that are larger than the index type size for the pointer being
analysed. This will add a couple of tests to show what happens both when
using a smaller and larger index type, and when having out-of-bounds
indices (both too large and negative).