[clang] [BoundsSafety][NFC] Add the count-refill logic for late-parsed bounds attributes (PR #224545)

[Yeoul Na via cfe-commits]

rapidsna wrote:

Superseded: reopening from `users/` branches so the PRs can form a GitHub stack (PRs from forks cannot be stacked).

https://github.com/llvm/llvm-project/pull/224545