[clang] [clang] LazyOffsetPtr: Use native pointer width (PR #111995)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> > #112806 should address this without narrowing the field to 32 bits.
> 
> As does [#111995 (comment)](https://github.com/llvm/llvm-project/pull/111995#discussion_r1805329590), with less code and more generality

I prefer this solution too.

https://github.com/llvm/llvm-project/pull/111995