Make Gradle builds faster

[alexander-yevsyukov]

This is a meta issue and a checklist with tasks to make our Gradle builds faster across all repositories.

• (Ironically) Find a Gradle plugin that measures time required the whole build pass successfully.
  We need to measure what we do.

• Apply filtering for only io.spine.* artifacts when mavenLocal() is used
  according to advices from “The case for mavenLocal()”.

• Find out what it costs to use Gradle Enterprise (@alexander-yevsyukov is already on it).

• Analyze what detekt does to run its build faster.
  What do don't do what they do?

• Find other projects of Gradle plugins,
  and see what they do about testing their plugins. What do we need to change the way we work?

• We also need to Run builds at GitHub faster #426.
  We update subprojects often. We wait for publishing far too long.

[alexander-yevsyukov]

@armiol, @dmdashenkov, @yevhenii-nadtochii, FYI.

[alexander-yevsyukov]

Gradle Doctor helps in some of the things we need.