[llvm] [ADT] Refactor DenseMapInfo for integer types (NFC) (PR #155549)

[Vitaly Buka via llvm-commits]

vitalybuka wrote:

> @kazutakahirata I am going to revert to fix our bots?

Or maybe not, https://github.com/llvm/llvm-project/pull/155826 probably works

https://github.com/llvm/llvm-project/pull/155549