Auto merge of #113606 - jyn514:parallel-compiler-cleanup, r=cjgillot

Don't require each rustc_interface tool to opt-in to parallel_compiler

Previously, forgetting to call `interface::set_thread_safe_mode` would cause the following ICE:
```
thread 'rustc' panicked at 'uninitialized dyn_thread_safe mode!', /rustc/dfe0683138de0959b6ab6a039b54d9347f6a6355/compiler/rustc_data_structures/src/sync.rs:74:18
```

This calls `set_thread_safe_mode` in `interface::run_compiler` to avoid requiring it in the caller.

Fixes `tests/run-make-fulldeps/issue-19371` when parallel-compiler is enabled.

r? `@SparrowLii` cc rust-lang/rust#75760

Author: bors