Use scriv for CHANGELOG generation in release workflow

[jwodder]

Part of #6918.

[yarikoptic]

A few minor questions/comments. Otherwise -- looks worth trying! Thank you!

[codecov]

Codecov Report

Merging #7009 (22beee9) into maint (5767ee4) will increase coverage by 4.36%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##            maint    #7009      +/-   ##
==========================================
+ Coverage   71.83%   76.19%   +4.36%     
==========================================
  Files         354      354              
  Lines       58618    58751     +133     
  Branches     6613     6613              
==========================================
+ Hits        42108    44766    +2658     
+ Misses      16495    13970    -2525     
  Partials       15       15              

Impacted Files	Coverage Δ
datalad/cmd.py	75.33% <0.00%> (-4.44%)	⬇️
datalad/customremotes/tests/test_datalad.py	87.23% <0.00%> (-1.90%)	⬇️
datalad/_version.py	45.68% <0.00%> (-0.28%)	⬇️
datalad/distribution/create_sibling.py	60.48% <0.00%> (-0.15%)	⬇️
datalad/runner/runner.py	100.00% <0.00%> (ø)
datalad/cli/common_args.py	100.00% <0.00%> (ø)
datalad/support/tests/test_network.py	69.09% <0.00%> (+0.07%)	⬆️
datalad/customremotes/tests/test_archives.py	89.36% <0.00%> (+0.07%)	⬆️
datalad/support/gitrepo.py	84.25% <0.00%> (+0.11%)	⬆️
datalad/dochelpers.py	85.71% <0.00%> (+0.12%)	⬆️
... and 100 more

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[yarikoptic]

ok, and with this we will test if it all works -- added a release label. Thank you @jwodder

[yarikoptic-gitmate]

PR released in 0.17.6