Rather than using the tools manifest for opting-in to breaking a tool.

The rough plan: on master (but not beta or stable) the CI would ignore failing to build or test some tools (RLS, Clippy, etc). However, some bot would note when a tool started to fail and email interested parties (and/or display the info in a dashboard).

This should lower the friction for contributors working in the Rust repo when they make tool-breaking changes. However, we might miss some 'true positive' failure in the tools (e.g., #45820).