[DE-786] Run tests in parallel

[maciej-nedza]

Make tests run in parallel:

• runs on n threads where n is number of configured subdomains
• each thread gets its own subdomain
• test classes are run in parallel, but test methods are run sequentially
• there's one additional subdomain which can be preconfigured and not cleared, using it we can test stuff we couldn't test otherwise
• changed default test lifecycle to per class, to enable non-static BeforeAll. Without it, static parameters in base classes clashed in parallel test runs.
• there's @ResourceLock annotation which in theory could be used to fix the problem with shared resources, but when I've tested it, it was crashing due to thread pool limits. seems like it's not working with fixed=max thread pool size. Then we should just avoid static stuff.

[swarmia]

✅  Linked to Story DE-786 · Improve Java SDK tests execution on GitHub Actions because of long runs and timeouts
➡️  Part of Epic DE-1051 · SDK test coverage increased