Bumping to gradle 6

[upgle]

Description

• Gradle 5 uses Deprecated Typesafe Zinc compiler, and gradle 6.x supports SBT Zinc (Versions 1.2.0 and above.)
• Upgrade the version of akka-grpc-gradle-plugin for fixing compatibility issue with gradle 6.

Reference

• https://docs.gradle.org/current/userguide/scala_plugin.html#sec:configure_zinc_compiler

Related issue and scope

• I opened an issue to propose and discuss this change (#????)

My changes affect the following components

• General tooling

Types of changes

• Enhancement or new feature (adds new functionality).
• Breaking change (a bug fix or enhancement which changes existing behavior).

Checklist:

• I signed an Apache CLA.
• I reviewed the style guides and followed the recommendations (Travis CI will check :).
• I added tests to cover my changes.
• My changes require further changes to the documentation.
• I updated the documentation where necessary.

[style95]

Does this handle the annoying akka-grpc plugin logs issue?

[upgle]

No, this is for resolving compatibility issue with gradle 6.
This PR is for gradle version upgrade only and does not consider any other issues.

---

The problem you mentioned seems to be fixed in the akka-grpc 2.1.0 version.
I tried to upgrade the version, but the build does not work due to a dependency problem.

It would be better to deal with other PR.

https://github.com/akka/akka-grpc/releases/tag/v2.1.0
akka/akka-grpc#1363

[rabbah]

🎉 this is great thank you.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.18%. Comparing base (8843579) to head (65b84bf).
⚠️ Report is 137 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5276      +/-   ##
==========================================
- Coverage   80.09%   76.18%   -3.92%     
==========================================
  Files         238      238              
  Lines       14080    14199     +119     
  Branches      576      605      +29     
==========================================
- Hits        11277    10817     -460     
- Misses       2803     3382     +579     

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[style95]

LGTM with small questions.

[upgle]

Fixed all dependency issues. No code changes and all test code passed, so I'll merge it soon.

In my development environment (Intellij June 21, 2022), there is an issue that a full build is made even if one line of test code is modified. The new zinc compiler with gradle 6 doesn't have that problem, and this PR improves productivity.