Add src/test/java and src/test/kotlin by default in PlainDetekt

[BraisGabin]

We aren't adding the source sets src/test/java and src/test/kotlin in the PlainDetekt. It have little sense that we don't add those by default because our default configuration take those sources into account.

[codecov]

Codecov Report

Merging #3649 (b59ba33) into main (1c140c8) will decrease coverage by 0.03%.
The diff coverage is 0.00%.

❗ Current head b59ba33 differs from pull request most recent head 2f6116b. Consider uploading reports for the commit 2f6116b to get more accurate results

@@             Coverage Diff              @@
##               main    #3649      +/-   ##
============================================
- Coverage     78.12%   78.08%   -0.04%     
  Complexity     2836     2836              
============================================
  Files           467      467              
  Lines          9142     9146       +4     
  Branches       1737     1737              
============================================
  Hits           7142     7142              
- Misses         1058     1062       +4     
  Partials        942      942              

Impacted Files	Coverage Δ	Complexity Δ
...ab/arturbosch/detekt/extensions/DetektExtension.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)

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[chao2zhang]

It have little sense that we don't add those by default because our default configuration take those sources into account.

Agree 👍

[cortinico]

This is something we want to mention specifically in the changelog right? I expect users that are using the default config to get a lot of violation for their tests: #3102 (comment)

[BraisGabin]

Agree, this is not housekeeping