Evaluate helper function / custom adapter to format hex with dynamic length

This pattern is used frequently, maybe it makes sense to extract this into a helper function / add a custom adapter (local to DebugInfo/DWARF?)? This would avoid confusion with `0x{0:x-}`.
Maybe it could support omitting `0x` to adopt wider use.

_Originally posted by @s-barannikov in https://github.com/llvm/llvm-project/pull/191988#discussion_r3078217470_

The issue points to DebugInfo/DWARF but names no file, entry point, or test. Search that area for repeated dynamic hex-formatting patterns and the `0x{0:x-}` usage, then compare the helper and custom-adapter approaches, including whether omitting `0x` should be supported; done means agreeing on a scoped design and its validation path.

Written by the indexing model from the issue text.