ThrowingExceptionInMain: fix #2248 and add tests

[schalkms]

Fixes #2248

[codecov-io]

Codecov Report

Merging #2240 into master will increase coverage by 0.04%.
The diff coverage is 60%.

@@             Coverage Diff              @@
##             master    #2240      +/-   ##
============================================
+ Coverage     81.37%   81.41%   +0.04%     
- Complexity     2073     2077       +4     
============================================
  Files           343      345       +2     
  Lines          5981     5989       +8     
  Branches       1086     1084       -2     
============================================
+ Hits           4867     4876       +9     
  Misses          532      532              
+ Partials        582      581       -1

Impacted Files	Coverage Δ	Complexity Δ
...detekt/rules/exceptions/ThrowingExceptionInMain.kt	83.33% <50%> (+13.33%)	6 <4> (-4)	⬇️
.../gitlab/arturbosch/detekt/rules/MethodSignature.kt	50% <66.66%> (-10%)	0 <0> (ø)
...turbosch/detekt/rules/style/UnusedPrivateMember.kt	93.47% <0%> (ø)	5% <0%> (ø)	⬇️
...osch/detekt/rules/bugs/WrongEqualsTypeParameter.kt	100% <0%> (ø)	10% <0%> (+3%)	⬆️
...rmatting/wrappers/NoEmptyFirstLineInMethodBlock.kt	100% <0%> (ø)	2% <0%> (?)
...ch/detekt/formatting/wrappers/EnumEntryNameCase.kt	100% <0%> (ø)	2% <0%> (?)
...itlab/arturbosch/detekt/core/ProcessingSettings.kt	89.83% <0%> (+0.17%)	19% <0%> (+1%)	⬆️
...osch/detekt/api/internal/KotlinEnvironmentUtils.kt	86.27% <0%> (+0.27%)	0% <0%> (ø)	⬇️
.../io/gitlab/arturbosch/detekt/cli/runners/Runner.kt	87.23% <0%> (+0.27%)	10% <0%> (ø)	⬇️
...ab/arturbosch/detekt/formatting/KtLintMultiRule.kt	87.75% <0%> (+0.52%)	6% <0%> (ø)	⬇️
... and 1 more

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[BraisGabin]

The test does not report top level main functions with a wrong signature has the same problem. I know that you didn't change it, but it would be good to fix it too,