feat!: create alias when renaming an import.
Closes#15858
Implemented:
- [x] - Prevent using `reserved` keywords (e.g self) and `_`.
- [x] - Rename other modules that might be referencing the import.
- [x] - Fix "broken" tests.
- [ ] - Rename **only** "direct" references.
- [ ] - Test more cases.
Future possibilities:
1. Also support `extern crate <name>` syntax.
2. Allow aliasing `self` when it is inside an `UseTreeList`.
~3. If import path already has an alias, "rename" the alias.~
~[4. Create alias even if path is not the last path segment.](https://github.com/rust-lang/rust-analyzer/pull/16489#issuecomment-1930541697)~
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