Improve policy detailspage and add tests for policy detailspage and details

[sarahd93]

Checklist:

• Tests
• CHANGELOG Entry

[codecov]

Codecov Report

Merging #1593 into master will increase coverage by 1.4%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #1593     +/-   ##
=========================================
+ Coverage   37.97%   39.38%   +1.4%     
=========================================
  Files        1044     1044             
  Lines       23924    23902     -22     
  Branches     6596     6589      -7     
=========================================
+ Hits         9086     9414    +328     
+ Misses      13491    13178    -313     
+ Partials     1347     1310     -37

Impacted Files	Coverage Δ
gsa/src/web/pages/scanconfigs/detailspage.js	53.19% <100%> (+21.27%)	⬆️
gsa/src/web/pages/policies/detailspage.js	100% <100%> (+66.66%)	⬆️
gsa/src/web/pages/permissions/component.js	15.78% <0%> (+14.47%)	⬆️
gsa/src/web/components/section/header.js	100% <0%> (+15.38%)	⬆️
gsa/src/web/pages/policies/component.js	30.93% <0%> (+29.66%)	⬆️
gsa/src/web/entity/permissions.js	42.02% <0%> (+31.88%)	⬆️
gsa/src/web/components/icon/listicon.js	100% <0%> (+33.33%)	⬆️
gsa/src/web/components/icon/manualicon.js	100% <0%> (+33.33%)	⬆️
... and 14 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4ffcf6d...a3e87a3. Read the comment docs.

[bjoernricks]

Looks very good. Just one minor thing. I guess you can remove all the store.dispatch(entityActions.success('12345', policy)); calls. I don't think they are used nor required anymore.