Adds a test for nested proc-macro calls where the inner macro returns an
empty TokenStream.
This previously caused an ICE in rustc_resolve.

Since they became alumni and don't want to receive pings anymore.

…e-cargo}` to `compiler`

So that I don't become the only automatically-assigned reviewer due to
weighting reasons.

So that there's `n > 1` selection pool in case one of the eligible
reviewers go off rotation.

…ethercote

Tweak wording of diff marker diagnostic

…thercote

test and document that `proc_macro::Ident` is NFC-normalized

Previously, this was not tested at all and the test suite would pass even when replacing the `normalize_and_validate_ident` implementation with a `panic!`.

Add regression test for issue rust-lang#99173

Close rust-lang#99173.

Adds a regression test for rust-lang#99173, which was an ICE that occurred when a proc-macro generated code that invoked another proc-macro returning an empty `TokenStream`.

Update triagebot config for `compiler-errors`, `tests/{run-make,run-make-cargo}` and `fallback` adhoc_group

- Commit 1: Updates triagebot entries for `compiler-errors` (context: rust-lang/team#2205)
- Commit 2: Expand `tests/{run-make,run-make-cargo}` reviewer pool to the `compiler` `adhoc_group` instead of just me for weighting reasons, so I don't become the sole assigned reviewer even when I'm off rotation.
- Commit 3: Add myself to `fallback` adhoc_group so there's `n > 1` pool there, in case one of the reviewers go off rotation.