Restore coverage upload to codecov (falls back to legacy uploader), add coveralls upload

[bernhardkaindl]

Two commits here:

• they don't overlap the same lines
• They make their change twice because we upload coverage with the python2.7 and python3. to coverage databases (coverity.io / coveralls.io)
• they only alternate within the same file

The commits are:

• CodeCov: Use the CLI if the token is set, else the legacy action
  • restores coverage upload to coverity:
    • the new uploaded needs the Codecov Upload Token that isn't set up yet, restores coverity upload
    • Upload to Coverity is fixed, but does not show the coverage because the fork-point of this PR had no working coverage upload to compare coverage against.
• Coveralls: Add coverage upload to coveralls.io

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (eb9a639) 85.55% compared to head (01fc023) 86.95%.
Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #71      +/-   ##
==========================================
+ Coverage   85.55%   86.95%   +1.39%     
==========================================
  Files          16       17       +1     
  Lines        2021     2138     +117     
==========================================
+ Hits         1729     1859     +130     
+ Misses        292      279      -13     

Flag	Coverage Δ
python2.7	85.57% <100.00%> (+1.51%)	⬆️
python3.10.13	86.28% <100.00%> (+1.56%)	⬆️

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