[clang] Replace uses of CGBuilderTy::CreateElementBitCast (NFC)

* Add `Address::withElementType()` as a replacement for
  `CGBuilderTy::CreateElementBitCast`.

* Partial progress towards replacing `CreateElementBitCast`, as it no
  longer does what its name suggests. Either replace its uses with
  `Address::withElementType()`, or remove them if no longer needed.

* Remove unused parameter 'Name' of `CreateElementBitCast`

Reviewed By: barannikov88, nikic

Differential Revision: https://reviews.llvm.org/D153196