Auto merge of #116818 - Nilstrieb:stop-submitting-bug-reports, r=wesl…

…eywiser

Stop telling people to submit bugs for internal feature ICEs

This keeps track of usage of internal features, and changes the message to instead tell them that using internal features is not supported.

I thought about several ways to do this but now used the explicit threading of an `Arc<AtomicBool>` through `Session`. This is not exactly incremental-safe, but this is fine, as this is set during macro expansion, which is pre-incremental, and also only affects the output of ICEs, at which point incremental correctness doesn't matter much anyways.

See [MCP 620.](rust-lang/compiler-team#596)

![image](https://github.com/rust-lang/rust/assets/48135649/be661f05-b78a-40a9-b01d-81ad2dbdb690)