Enable JaCoCo and generate test coverage report

As part of quality control initiative and improve visibility of test coverage, this PR get correct test coverage of unit tests with JaCoCo.

Generate test coverage when test is executed
Gather all test coverage for parallel run in CI, multiple run (Pg,H2), sub projects.
Upload the test coverage file to artifact jacoco-all
Generate test coverage report and upload to artifact jacoco-report
Integration tests (digda-tests) is out of scope
Set up browsing site is out of scope. (Will be set later)

treasure-data / digdag