deprecations setuptools

[mdonadoni]

• ci(pytest): invoke pytest directly instead of setup.py test (deprecations setuptools #284)
• build(python): remove deprecated pytest-runner (deprecations setuptools #284)
• build(python): use optional deps instead of tests_require (deprecations setuptools #284)
• build(python): add minimal pyproject.toml (deprecations setuptools #284)
• build(docker): pin setuptools to v70 (deprecations setuptools #284)

Closes reanahub/reana#814

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 1.26%. Comparing base (db5508d) to head (6dc9f26).
Report is 7 commits behind head on master.

Additional details and impacted files

@@          Coverage Diff           @@
##           master    #284   +/-   ##
======================================
  Coverage    1.26%   1.26%           
======================================
  Files          10      10           
  Lines         555     555           
======================================
  Hits            7       7           
  Misses        548     548