Execute tests in parallel

[Goooler]

https://docs.gradle.org/8.0/userguide/performance.html#execute_tests_in_parallel

[codecov]

Codecov Report

Merging #5944 (52289e5) into main (a3dfea2) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #5944   +/-   ##
=========================================
  Coverage     84.48%   84.48%           
  Complexity     3788     3788           
=========================================
  Files           546      546           
  Lines         12937    12937           
  Branches       2275     2275           
=========================================
  Hits          10930    10930           
  Misses          877      877           
  Partials       1130     1130           

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[3flex]

I'm not sure why I haven't tried this earlier!

I think we should be a bit less aggressive though and use the suggestion from the Gradle docs which caps forks to half the processor count at most.

[Goooler]

I believe we can use Runtime.getRuntime().availableProcessors() on CI, which means full cores, there are 2 cores in GHA runners, use (Runtime.getRuntime().availableProcessors() / 2).takeIf { it > 0 } ?: 1 (result is 1) here seems to be less improvement on CI.

[3flex]

I was thinking about local builds. Maybe make it conditional on CI environment variable to use all cores in CI but not when building locally.