Use symbols for several tools

[uhafner]

Symbols will automatically switch color based on the selected theme.

Followup to jenkinsci/font-awesome-api-plugin#176

[codecov]

Codecov Report

Merging #1356 (85c65f1) into master (670dfe7) will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #1356      +/-   ##
============================================
+ Coverage     79.78%   79.87%   +0.08%     
- Complexity     1448     1453       +5     
============================================
  Files           251      252       +1     
  Lines          5611     5615       +4     
  Branches        427      427              
============================================
+ Hits           4477     4485       +8     
+ Misses          983      979       -4     
  Partials        151      151              

Impacted Files	Coverage Δ
...plugins/analysis/core/model/IconLabelProvider.java	100.00% <ø> (ø)
...alysis/core/model/StaticAnalysisLabelProvider.java	79.36% <ø> (ø)
...ins/plugins/analysis/core/model/DetailFactory.java	97.70% <100.00%> (-0.06%)	⬇️
...jenkins/plugins/analysis/core/model/JobAction.java	68.62% <100.00%> (ø)
...s/analysis/core/model/SymbolIconLabelProvider.java	100.00% <100.00%> (ø)
...lugins/analysis/warnings/DuplicateCodeScanner.java	84.76% <100.00%> (ø)
.../jenkins/plugins/analysis/warnings/ErrorProne.java	100.00% <100.00%> (ø)
...io/jenkins/plugins/analysis/warnings/SpotBugs.java	83.33% <100.00%> (+3.33%)	⬆️
...ins/plugins/analysis/warnings/tasks/OpenTasks.java	40.25% <100.00%> (ø)
...a/io/jenkins/plugins/analysis/core/model/Tool.java	76.74% <0.00%> (+2.32%)	⬆️
... and 1 more

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more