9773: internal: Improve `extract_function` assist r=Veykril a=Veykril
- fix: It doesn't try to overwrite parts of selected comments any longer
- fix: It doesn't wrap tail expressions and return types in a result or option unnecessarily
- feat?: It now adds a `const` modifier to the created function if extract somethings from a const context
Fixes#7840
Co-authored-by: Lukas Wirth <lukastw97@gmail.com>
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