Refactor KotlinCoreEnvironment test setup

[schalkms]

This PR adds an extension function to Root to automatically create and
dispose the KotlinCoreEnvironment for testing purposes.
The objects in the KotlinCoreEnvironment are wrapped to simplify the
object creation and disposal.

[codecov-io]

Codecov Report

Merging #1880 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1880      +/-   ##
============================================
- Coverage      80.3%   80.25%   -0.06%     
+ Complexity     1958     1949       -9     
============================================
  Files           325      325              
  Lines          5519     5504      -15     
  Branches       1026     1019       -7     
============================================
- Hits           4432     4417      -15     
  Misses          557      557              
  Partials        530      530

Impacted Files	Coverage Δ	Complexity Δ
...bosch/detekt/rules/style/UnnecessaryParentheses.kt	80% <0%> (-12.31%)	4% <0%> (-13%)
.../gitlab/arturbosch/detekt/rules/ThrowExtensions.kt	75% <0%> (-5%)	0% <0%> (ø)
...urbosch/detekt/generator/collection/RuleVisitor.kt	87.23% <0%> (-0.81%)	38% <0%> (+2%)
...n/io/gitlab/arturbosch/detekt/api/ConsoleReport.kt	100% <0%> (ø)	5% <0%> (+2%)	⬆️
...ab/arturbosch/detekt/rules/style/WildcardImport.kt	84.61% <0%> (ø)	5% <0%> (ø)	⬇️
...ch/detekt/rules/style/ExplicitItLambdaParameter.kt	100% <0%> (ø)	4% <0%> (ø)	⬇️
...n/io/gitlab/arturbosch/detekt/rules/LinesOfCode.kt	100% <0%> (ø)	0% <0%> (ø)	⬇️
...io/gitlab/arturbosch/detekt/rules/IsPartOfUtils.kt	100% <0%> (ø)	0% <0%> (ø)	⬇️
...itlab/arturbosch/detekt/rules/style/MagicNumber.kt	89.74% <0%> (+1.28%)	60% <0%> (-1%)	⬇️

---

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 82f5e06...b94c31e. Read the comment docs.