[clang] [clang-format] Hanlde qualified type name for `QualifierAlignment` (PR #125327)

[Owen Pan via cfe-commits]

owenca wrote:

> Seems to also work for top-level types (`::int_64_t constexpr x{123};` works correctly) but breaks for fully qualified types (`::std::int64_t constexpr x{123};` becomes `::constexpr std::int64_t x{123};`)

Yeah, I intentionally didn't want to use a loop for names like `A1::A2:: ... ::An` and instead just wanted to handle single-level nested names like `A::B`.

https://github.com/llvm/llvm-project/pull/125327