Rollup of 10 pull requests
Successful merges:
- #52946 (Documented impl From on line 367 of libserialize/json.rs)
- #53234 (Remove Travis shutdown debug scripts, and remove CI-specific DNS settings)
- #53313 (Two small improvements)
- #53360 (Addressed #51602)
- #53364 (Warn if the user tries to use GATs)
- #53373 (Tweak unclosed delimiter parser error)
- #53377 (std: Use target_pointer_width for BACKTRACE_ELF_SIZE)
- #53395 (Use #[non_exhaustive] on internal enums)
- #53399 (Tidy: ignore non-Markdown files when linting for the Unstable Book)
- #53412 (syntax_ext: remove leftover span_err_if_not_stage0 macro.)
b2028828db