ConstantArrayType does not expose Size method from Clang

[Ninja3047]

The clang ConstantArrayType has a getSize method which returns the number of elements in the array as an APInt but this is not exposed on the multiplier side. A workaround is to get the total size of the Type and divide it by the size of the element.

[pgoodman]

This issue ultimately traces its roots back to PASTA. There, we'd perhaps want to add support for APInt in the form of gap multiprecision integers, so that PASTA's public API (headers) remains clang/llvm-dependency free.