Rollup merge of #109926 - SparrowLii:parallel_log, r=eholk

write threads info into log only when debugging

The current tracing log will unconditionally write thread information during parallel compilation, which sometimes confuses some normal output log information

This fixes the UI test failure of:
```
[ui] tests/ui/consts/const_in_pattern/issue-73431.rs
```
Updates #75760

Author: JohnTitor

compiler/rustc_log/src/lib.rs

@@ -83,7 +83,7 @@ pub fn init_env_logger(env: &str) -> Result<(), Error> {
         .with_verbose_exit(verbose_entry_exit)
         .with_verbose_entry(verbose_entry_exit)
         .with_indent_amount(2);
-    #[cfg(parallel_compiler)]
+    #[cfg(all(parallel_compiler, debug_assertions))]
     let layer = layer.with_thread_ids(true).with_thread_names(true);
 
     let subscriber = tracing_subscriber::Registry::default().with(filter).with(layer);

src/librustdoc/lib.rs

@@ -203,7 +203,7 @@ fn init_logging() {
         .with_verbose_exit(true)
         .with_verbose_entry(true)
         .with_indent_amount(2);
-    #[cfg(parallel_compiler)]
+    #[cfg(all(parallel_compiler, debug_assertions))]
     let layer = layer.with_thread_ids(true).with_thread_names(true);
 
     use tracing_subscriber::layer::SubscriberExt;