Add option to return new (possibly lazy) signal instead of operating inplace

[hakonanes]

Description of the change

This PR adds the option to pass inplace=False to many methods, like EBSD.remove_static_background() or EBSDMasterPattern.rescale_intensity(). Most methods also support to return a lazy signal instead of one in memory via lazy_output=True.

A LazyVirtualBSEImage class is added for use with mostly VirtualBSEImage.rescale_intensity(inplace=False, lazy_output=True).

Progress of the PR

• [x] Docstrings for all functions
• [x] Unit tests with pytest for all lines
• [x] Clean code style by running black via pre-commit

Minimal example of the bug fix or new feature

>>> import kikuchipy as kp
>>> s = kp.data.nickel_ebsd_small()

# Before

>>> s2 = s.deepcopy()
>>> s2.remove_static_background()

# Now

>>> s2 = s.remove_static_background(inplace=False)

For reviewers

• [ ] The PR title is short, concise, and will make sense 1 year later.
• [ ] New functions are imported in corresponding __init__.py.
• [ ] New features, API changes, and deprecations are mentioned in the unreleased section in CHANGELOG.rst.
• [ ] New contributors are added to release.py, .zenodo.json and .all-contributorsrc with the table regenerated.