Simplify dataset downloads and add more EBSD master patterns

Description of the change

The following EBSD master patterns, simulated with EMsoft, can now be downloaded from Zenodo (https://zenodo.org/communities/ebsd/?page=1&size=20) via kikuchipy.data.ebsd_master_pattern():

Al
Si
Ni
Austenite
Ferrite
Chi-phase in steel
Sigma-phase in steel

The high resolution Si patterns available from silicon_ebsd_moving_screen_x(), where "x" is either "in", "out5mm" or "out10mm", should now be downloaded from si_ebsd_moving_screen(distance), where distance is 0 (in), 5 or 10. The old functions are deprecated and will be removed in version 0.9.

The 10 Ni datasets acquired with varying gain are made available from ni_gain(number) and ni_gain_calibration(number), where number is one of 1-10.

Documentation is updated accordingly.

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

# Ni gain patterns

>>> s1 = kp.data.ni_gain(1, allow_download=True)
>>> s10 = kp.data.ni_gain(10, allow_download=True)
>>> s6_cal = kp.data.ni_gain_calibration(6, allow_download=True)

# Si moving screen patterns

>>> s_si = kp.data.si_ebsd_moving_screen(10, allow_download=True)

# EBSD master patterns

>>> mp_chi = kp.data.ebsd_master_pattern("steel_chi", allow_download=True, projection="lambert")
>>> mp_al = kp.data.ebsd_master_pattern("al", allow_download=True, energy=20)

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.

pyxem / kikuchipy