Refactor Gradle integration tests

[picklebento]

This PR serves two purposes:

• Move all Gradle integration tests to use the Gradle testkit API. There is no more unit test depending on Gradle internal API itself.
  • One benefit is less maintenance over the future Gradle upgrade
  • Another benefit is that after Refactor integration test for detekt-gradle-plugin #3356, IntelliJ is not really working with the new intTest source set and we cannot launch those tests in IDE. IDEA-218815 is an issue that's applicable to a lot of people in the recent versions. So I am planning to remove the intTest and merge it back to test.
• Set up testing infrastructure for Refactor detekt-gradle-plugin off com.android.tools.build:gradle #3327 and I did verify that the RFC in [RFC] Register Detekt tasks based on source set for Android #3334 is actually not working :)

Note

While this mostly maintains the test coverage, I did reduce the following test cases:

• Test for com.android.test is removed. Since there are many other plugin's like com.android.dynamic-feature, com.android.lint and com.android.reporting, it is not necessary to test all different android plugins. As long as the base plugin com.android.build.gradle.api.AndroidBasePlugin is applied, we do not need to worry too much about other subplugins.
• Removed one flavor dimension sally from name. This does not provide too much value in my opinion while contributes significantly the lines of code in tests.

[codecov]

Codecov Report

Merging #3489 (7d020ab) into master (8350ce2) will decrease coverage by 0.78%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #3489      +/-   ##
============================================
- Coverage     80.52%   79.74%   -0.79%     
+ Complexity     2888     2864      -24     
============================================
  Files           459      459              
  Lines          8643     8643              
  Branches       1674     1674              
============================================
- Hits           6960     6892      -68     
- Misses          763      841      +78     
+ Partials        920      910      -10     

Impacted Files	Coverage Δ	Complexity Δ
...gitlab/arturbosch/detekt/internal/DetektAndroid.kt	0.00% <0.00%> (-71.88%)	0.00% <0.00%> (-12.00%)
.../io/gitlab/arturbosch/detekt/internal/DetektJvm.kt	0.00% <0.00%> (-59.26%)	0.00% <0.00%> (-5.00%)
...ab/arturbosch/detekt/extensions/DetektExtension.kt	42.85% <0.00%> (-9.53%)	2.00% <0.00%> (-5.00%)
...tlab/arturbosch/detekt/extensions/DetektReports.kt	35.29% <0.00%> (-5.89%)	5.00% <0.00%> (-1.00%)
...kotlin/io/gitlab/arturbosch/detekt/DetektPlugin.kt	82.22% <0.00%> (-4.45%)	10.00% <0.00%> (ø%)
.../main/kotlin/io/gitlab/arturbosch/detekt/Detekt.kt	26.26% <0.00%> (-1.02%)	19.00% <0.00%> (-1.00%)

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[BraisGabin]

👏🏻👏🏻 Nice refactor. I had no idea that detektMain was running the android tasks too. Nor the ignored configuration. I have work to do Monday morning at work 😅.

[cortinico]

LGTM.
Just one note, should we merge #3453 before this?

[picklebento]

LGTM.
Just one note, should we merge #3453 before this?

Good call. Now we have one remaining non-testkit gradle unit test