[pyupgrade] Implement import-replacement rule (UP035)

[colin99d]

A part of #827. I started this trying to use libcst. However, if found it added a lot of complexity because I have to change the order of the imports, which really messed up the formatting. If you know of a good way to handle this I will be happy to switch.

[colin99d]

@charliermarsh , I don't love the way I am handling muli-line imports. Pretty much, if there is a match I am always changing it to:

from unmatching (
    import1,
    import2
)
from matching {
    import1
    import2
)

However, I think this might be the best way for a few reasons:

1. Libcst makes this a lot more complicated (unless there is something I am missing)
2. If we are adding our own version of black, it makes sense for these functions to export in one standard way, and then let black clean up the change
3. This standardizes all ruff code, which may be beneficial

[colin99d]

I am moving this out of draft status. However, I will still be adding some more test cases to make sure it always works.

[colin99d]

@charliermarsh what else do you want here for a merge (im not sure why only the windows texts are failing).

[charliermarsh]

@colin99d - Nothing on your end. I just need to find time to review. Sorry for the delay. I'll rebase etc. when necessary.

[colin99d]

Perfect! Just wanted to make sure you weren't waiting on something. Thank you for all the work you put into this!

[colin99d]

@charliermarsh I got all the six stuff removed, would you like me to add a blurb in the readme about why we do not have six, and how users can run pyupgrade once, and then use us?

[charliermarsh]

@colin99d - No that's ok. I'll add something to BREAKING_CHANGES.md and the release notes prior to release.

[charliermarsh]

I want to change one more thing here, but hopefully it can go out tomorrow.