Consolidate packaging in pyproject.toml

[ericpre]

Needs hyperspy/hyperspy#3252 to work in editable installation mode (pip -e). Non-editable pip installation works fine.
The motivation for this changes to consolidate package metadata in pyproject.toml and use modern package building approach, which are now fairly well established.

Progress of the PR

• Consolidate packaging in pyproject.toml and remove setup.py,
• fix formatting,
• [n/a] docstring updated (if appropriate),
• [n/a] update user guide (if appropriate),
• [n/a] added tests,
• added line to CHANGES.rst,
• ready for review.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b8c0de6) 91.75% compared to head (165217d) 91.87%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #10      +/-   ##
==========================================
+ Coverage   91.75%   91.87%   +0.11%     
==========================================
  Files          69       67       -2     
  Lines        7279     7274       -5     
==========================================
+ Hits         6679     6683       +4     
+ Misses        600      591       -9     

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