Setup sourcegraph for scala 3

[ghostbuster91]

This PR apart from adding integration with sourcegraph also unifies how java is being set. The unification part can be revert or done otherwise if desired.

actions/setup-java@v1 supports only one distribution - Zulu OpenJDK (Note that v2 supports wider variety of distributions) That means PR also changes openjdk distro which is used by the CI pipeline.

While I believe that both changes (unification and switch to Zulu) are beneficial I can agree that they might be split into multiple PRs for better transparency (if needed).