[clang] [clang] Rework `hasBooleanRepresentation`. (PR #136038)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> Putting aside for now the naming issue ([#136038 (comment)](https://github.com/llvm/llvm-project/pull/136038#discussion_r2049703902)), is there anything left for the changes proposed in this PR?

Based on:

> ... but I think "will this end up as an i1" is a fair summary.

I think this probably should include 1-bit bit-precise integer types in `hasBooleanRepresentation()`, but it may not be critical.

https://github.com/llvm/llvm-project/pull/136038