fix: correctly restore type-only import/export names

[kricsleo]

resolves #311

This is a rework of PR: #333 🫡

• Address more edge cases (see the added testcase)
• Using AssignmentExpression to record the type-only hints (Instead of renaming import/export variables previously, since it's unstable and has some minor flaws.)
• Merge ExportFixer into TypeOnlyFixer since it's now part of TypeOnlyFixer's responsibilities
• Separate type-only and value import/export statements
• Make the type-only fix easier to understand and maintian

[kricsleo]

I’ve got to say, it’s been really tough for me trying to figure out how to implement this feature 🥲🥲

Hope to hear your feedback ❤️

[Swatinem]

To be quite honest, I haven’t really been maintaining this project for years, so I’m not that familiar with the code anymore myself to be of much help here.

But I do trust the testsuite quite a bit, and the results look good to me.