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

Merging #5276 (65b84bf) into master (8843579) will decrease coverage by 3.91%.
The diff coverage is n/a.

@@            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     

Impacted Files	Coverage Δ
...che/openwhisk/core/loadBalancer/LeanBalancer.scala	0.00% <ø> (ø)
...core/database/cosmosdb/RxObservableImplicits.scala	0.00% <0.00%> (-100.00%)	⬇️
...ore/database/cosmosdb/cache/CacheInvalidator.scala	0.00% <0.00%> (-100.00%)	⬇️
...e/database/cosmosdb/cache/ChangeFeedConsumer.scala	0.00% <0.00%> (-100.00%)	⬇️
...core/database/cosmosdb/CosmosDBArtifactStore.scala	0.00% <0.00%> (-95.85%)	⬇️
...sk/core/database/cosmosdb/CosmosDBViewMapper.scala	0.00% <0.00%> (-93.90%)	⬇️
...tabase/cosmosdb/cache/CacheInvalidatorConfig.scala	0.00% <0.00%> (-92.31%)	⬇️
...enwhisk/connector/kafka/KamonMetricsReporter.scala	0.00% <0.00%> (-83.34%)	⬇️
...e/database/cosmosdb/cache/KafkaEventProducer.scala	0.00% <0.00%> (-78.58%)	⬇️
...whisk/core/database/cosmosdb/CosmosDBSupport.scala	0.00% <0.00%> (-74.08%)	⬇️
... and 55 more

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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.