Inline all format arguments where possible

This makes code more readale and concise,
moving all format arguments like `format!("{}", foo)`
into the more compact `format!("{foo}")` form.

The change was automatically created with, so there are far less change
of an accidental typo.

```
cargo clippy --fix -- -A clippy::all -W clippy::uninlined_format_args
```

crates/sourcegen/src/lib.rs

@@ -57,7 +57,7 @@ impl CommentBlock {
     pub fn extract(tag: &str, text: &str) -> Vec<CommentBlock> {
         assert!(tag.starts_with(char::is_uppercase));
 
-        let tag = format!("{}:", tag);
+        let tag = format!("{tag}:");
         // Would be nice if we had `.retain_mut` here!
         CommentBlock::extract_untagged(text)
             .into_iter()
@@ -163,7 +163,7 @@ pub fn reformat(text: String) -> String {
 }
 
 pub fn add_preamble(generator: &'static str, mut text: String) -> String {
-    let preamble = format!("//! Generated by `{}`, do not edit by hand.\n\n", generator);
+    let preamble = format!("//! Generated by `{generator}`, do not edit by hand.\n\n");
     text.insert_str(0, &preamble);
     text
 }