CI: Switch to mambaforge as  base image for Docker ENV build
- [x] closes #48142
Thanks @phofl  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 1.4.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 3de21defb3d99e1cf8abf7acf6da03c5301f80ac
```

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

```
git commit -am 'Backport PR #48143: CI: Switch to mambaforge as  base image for Docker ENV build'
```

4. Push to a named branch:

```
git push YOURFORK 1.4.x:auto-backport-of-pr-48143-on-1.4.x
```

5. Create a PR against branch 1.4.x, I would have named this PR:

> "Backport PR #48143 on branch 1.4.x (CI: Switch to mambaforge as  base image for Docker ENV build)"

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).
                