Auto merge of #13684 - unvalley:extract-expressions-from-format-string, r=Veykril

feat: extract_expressions_from_format_string

closes #13640
- rename to `extract_expressions_from_format_string`
- leave identifier from format string
	- but this is from rustc version 1.65.0
	- Should I add flag or something?

Note: the assist behaves below cases for now. I'll create an issue for these.
```rs
let var = 1 + 1;
// ok
format!("{var} {1+1}");   // → format!("{var} {}", 1+1);
format!("{var:?} {1+1}"); // → format!("{var:?} {}", 1 + 1);
format!("{var} {var} {1+1}"); // → format!("{var} {var} {}", 1 + 1);

// breaks (need to handle minimum width by postfix`$`)
format!("{var:width$} {1+1}"); // → format!("{var:width\$} {}", 1+1);
format!("{var:.prec$} {1+1}"); // → format!("{var:.prec\$} {}", 1+1);
format!("Hello {:1$}! {1+1}", "x" 5); // → format("Hello {:1\$}! {}", "x", 1+1);
format!("Hello {:width$}! {1+1}", "x", width = 5); // → println!("Hello {:width\$}! {}", "x", 1+1);
```

https://user-images.githubusercontent.com/38400669/204344911-f1f8fbd2-706d-414e-b1ab-d309376efb9b.mov

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