Support Gradle config cache in detekt's build

[3flex]

A few improvements to eventually allow the Gradle configuration cache to be used when building detekt.

There are changes required in some Gradle plugins used by the detekt build before this will work:

• Kotlin 1.4.30 or higher
• Gradle 7.0 (or 6.8.4 which should include a backported fix for an issue)
• Consider supporting Gradle's configuration cache Kotlin/dokka#1217 to be fixed
• Support Gradle's configuration cache Kotlin/binary-compatibility-validator#50 to be merged & released

[codecov]

Codecov Report

Merging #3574 (fa556ae) into main (aa46448) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #3574   +/-   ##
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  Coverage     77.53%   77.53%           
  Complexity     2835     2835           
=========================================
  Files           464      464           
  Lines          8779     8779           
  Branches       1720     1720           
=========================================
  Hits           6807     6807           
  Misses         1046     1046           
  Partials        926      926           

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[picklebento]

Did you mean to turn on org.gradle.unsafe.configuration-cache=true? Or is this PR purely to fix issues to be prepared for the work?

[3flex]

It's just to fix issues in the build for now. As I mentioned there are third party Gradle plugin updates that are required first, but once they've made fixes and detekt updates those dependencies it should be OK to enable.

[BraisGabin]

@3flex should we have an issue to track the things that we need to do?