TST (string dtype): clean-up assorted xfails
An bunch of assorted xfails that were no longer needed or had a trivial fix

xref https://github.com/pandas-dev/pandas/issues/54792
Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

```
git checkout 2.3.x
git pull
```

2. Cherry pick the first parent branch of the this PR on top of the older branch:
```
git cherry-pick -x -m1 e7d1964ab7405d54d919bb289318d01e9eb72cd1
```

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

```
git commit -am 'Backport PR #60345: TST (string dtype): clean-up assorted xfails'
```

4. Push to a named branch:

```
git push YOURFORK 2.3.x:auto-backport-of-pr-60345-on-2.3.x
```

5. Create a PR against branch 2.3.x, I would have named this PR:

> "Backport PR #60345 on branch 2.3.x (TST (string dtype): clean-up assorted xfails)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the `Still Needs Manual Backport` label once the PR gets merged.

If these instructions are inaccurate, feel free to [suggest an improvement](https://github.com/MeeseeksBox/MeeseeksDev).
                 Manual backport -> https://github.com/pandas-dev/pandas/pull/60349