We have a handful of utils for emitting lints: span_lint, span_lint_and_help, etc. We'd like to replace these with one new util named span_clippy_lint. It was already implemented in #7668, but not yet merged.

Goals

• Be more consistent with rustc
• Potentially improve perf since allowed lints stop before computing output messages
• Enable trimmed paths (Enable trimmed paths #7798)

Question: Should we use .emit() like rustc, or use Drop to emit automatically?

Steps

• Add span_clippy_lint from Enable trimmed paths #7668 and patch the metadata collector to work with it
• Change all span_lint_* calls to span_clippy_lint
• divide this into smaller parts?
• Remove span_lint* utils and metadata collector support