[mlir] `remove-dead-values`: properly handle symbol users outside of a pass root. (#225355)
Follow up to the
https://github.com/llvm/llvm-project/pull/224831#pullrequestreview-5262450200
comment.
Add `areAllUsesVisible` query to the `SymbolUserMap` to check is all
users are visible and use it in `remove-dead-values`.