Add error prone checks for internal javadoc and private constructors

[jack-berg]

Ports build automation from opentelemetry-java-instrumentation/custom-checks to add additional custom error prone checks

• Ensure that utility classes have private constructors
• Ensure public internal classes have standard boilerplate

Resolves #6798.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.49%. Comparing base (2e8bf7f) to head (c8f04ed).
Report is 3 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@ ## main #6844 +/- ## ============================================ - Coverage 90.49% 90.49% -0.01%  Complexity 6598 6598 ============================================ Files 731 731 Lines 19735 19735 Branches 1938 1938 ============================================ - Hits 17860 17859 -1  Misses 1283 1283 - Partials 592 593 +1 

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[laurit]

did you deliberately keep the javaagent package?

[jack-berg]

Nope, good catch!