[clang] [clang][Interp] Integral pointers (PR #84159)

[Timm Baeder via cfe-commits]

tbaederr wrote:

FWIW I've been tracking test failures by enabling the new interpreter by default and running `ninja check-clang-{ast,sema,semacxx,codegen}` at https://tbaederr.github.io/stats/. With this patch, we're down from 281 to 262 (with only one new failure, `Sema/callingconv-cast.c`).

https://github.com/llvm/llvm-project/pull/84159