feat(config): make dask autoscaler configurable

[Alputer]

closes reanahub/reana#834

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 60.08%. Comparing base (15d0b97) to head (95ea2df).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
reana_server/rest/info.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #702      +/-   ##
==========================================
+ Coverage   60.06%   60.08%   +0.01%     
==========================================
  Files          32       32              
  Lines        3546     3550       +4     
==========================================
+ Hits         2130     2133       +3     
- Misses       1416     1417       +1     

Files with missing lines	Coverage Δ
reana_server/config.py	84.15% <100.00%> (+0.17%)	⬆️
reana_server/rest/info.py	76.00% <50.00%> (-1.09%)	⬇️

[tiborsimko]

See the comment about "true" vs "True" in reanahub/reana-workflow-controller#604 (comment)

[tiborsimko]

Commit log cosmetics: the conventional commit scope should represent which component was touched by the change, so we should use "config" here:

feat(config): make Dask autoscaler configurable (#835)

(Unfortunately the previous commit slipped with feat(helm) here even if this component does not have any Helm... We could override it using Release Please commit message overriding functionality to have nicer release news compilation.)

Also, please put Closes #NNN in the commit message body, so that we have the reference to the issue which this PR closes also locally, not only on GitHub.