ci: change error-prone check to be more explicit rather than based on $CI env variable

[rmuir]

Description

In the CI system, we want to suffer the pain of error-prone just for the "checks without tests" job.

When running the tests, we would prefer that compilation is fast (other job is using error-prone). For example on windows runner, significant portion of "tests" job is actually compilation:

Summary of top-20 task execution times (aggregated by unique name, possibly running in parallel):
 1344.83 sec.  test
 553.56 sec.  compileTestJava
 233.73 sec.  compileJava

It would be better to just pass something like a -Perrorprone in the "checks without tests" job, and don't pass it in the "tests" job?

[dweiss]

The option is there already -

-Pvalidation.errorprone=false

will turn off errorprone.

[dweiss]

try ./gradlew allOptions.

[rmuir]

Will make a PR and let's see if it makes a dent. Thank you

[rmuir]

I made a stab on #15312