BUG: Fix bug, where BooleanDtype columns are converted to Int64
- [x] closes #32287
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

@AnnaDaglis do you think you'll have time to update this soon? We're hoping to get 1.0.2 out in the next couple days. If not, no problem, we'll just move it to the next release. > Should this entire check be inside a big if not is_extension_array_dtype(input_array.dtype)? There aren't any cases where we want to convert from extension type to extension type, right?

Yes, right now, if the dtype is already an extension dtype, we don't want to change it (in the future, if there is eg a new nullable timestamp dtype, we might want to do this, but that is not yet relevant right now) Ha @AnnaDaglis I was just pushing the same changes here. Looks like we ran into the same issue with the Series.astype failing to copy.

Mind if I push some commits here? I think I tracked it down. I might end up just force pushing to your branch if that's OK. It'll mess some things up but will be easiest I think.  @TomAugspurger No problem! OK thanks! If you want to sync up, you can `git fetch origin` and then `git reset --hard origin/fix_convert_dtypes_bool` when you have that branch checked out locally. Hopefully we're good to go.

@jbrockmendel on master `Series.astype()` wasn't always copying for datetime64 dtypes. Those changes are in 934147b492d265cfd798c5288821f665c82a7a7c.
 nice catch thanks @AnnaDaglis very nice! @meeseksdev backport 1.0.x @meeseeksdev backport 1.0.x 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 1.0.x
$ git pull
```

2. Cherry pick the first parent branch of the this PR on top of the older branch:
```
$ git cherry-pick -m1 a2acd1b2c662e6ae87e923989df7c0c95444f6d7
```

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

```
$ git commit -am 'Backport PR #32490: BUG: Fix bug, where BooleanDtype columns are converted to Int64'
```

4. Push to a named branch :

```
git push YOURFORK 1.0.x:auto-backport-of-pr-32490-on-1.0.x
```

5. Create a PR against branch 1.0.x, I would have named this PR:

> "Backport PR #32490 on branch 1.0.x"

And apply the correct labels and milestones.

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

If these instruction are inaccurate, feel free to [suggest an improvement](https://github.com/MeeseeksBox/MeeseeksDev).
                 Huh, this seemingly wasn't backported, but the release notes are there... I'll do something manually. 