[feature] Differentiate between safe and unsafe fixes

This task tracks the work implementing safe and unsafe fixes as described in #1997. 

*Safe* fixes are fixes that don't change the semantics of the program. *Unsafe* fixes may change the program's semantics; therefore, we advise users to manually review and test the changes.

## Tasks 

* [x] #4182
* [x] #4183
* [x] #4340
* [x] #4276
* [x] #4184
* [x] #4185
* [x] #4186
* [x] #4187