REF: make Block.delete return a new Block
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [ ] whatsnew entry

I lost track of the original use case that motivated this, but in general i think we're better off keeping block.values fixed.
https://github.com/pandas-dev/pandas/runs/4989389923?check_suite_focus=true

are these unrelated? > are these unrelated?

Yes.  These were fixed in #45707 Nice.  Now #45352 is all that's left between us and block.values being immutable