add support for multi partition kafka topics

[bdoyle0182]

Description

This will add support to configure a certain topic class to have a specified number of partitions by including a partitions config in the configuration for that topic class. This currently does not include the consumer metric reporting for delay and lag since it assumes a single partition topic so it uses only partition 0 to emit that metric. But this change will unblock from attempting to use multiple partitions for your kafka topics by not having the producer use specify a key for the producer record such that the kafka messages are always hashed to the same consistent partition.

Related issue and scope

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

My changes affect the following components

• [ ] API
• [ ] Controller
• [X] Message Bus (e.g., Kafka)
• [ ] Loadbalancer
• [ ] Scheduler
• [ ] Invoker
• [ ] Intrinsic actions (e.g., sequences, conductors)
• [ ] Data stores (e.g., CouchDB)
• [ ] Tests
• [ ] Deployment
• [ ] CLI
• [ ] General tooling
• [ ] Documentation

Types of changes

• [ ] Bug fix (generally a non-breaking change which closes an issue).
• [X] Enhancement or new feature (adds new functionality).
• [ ] Breaking change (a bug fix or enhancement which changes existing behavior).

Checklist:

• [X] 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.

[codecov-commenter]

Codecov Report

Merging #5398 (291b3b2) into master (de3e0a8) will decrease coverage by 1.03%. The diff coverage is 100.00%.

:exclamation: Current head 291b3b2 differs from pull request most recent head db7e4c8. Consider uploading reports for the commit db7e4c8 to get more accurate results

@@            Coverage Diff             @@
##           master    #5398      +/-   ##
==========================================
- Coverage   76.83%   75.80%   -1.03%     
==========================================
  Files         240      240              
  Lines       14596    14596              
  Branches      672      671       -1     
==========================================
- Hits        11215    11065     -150     
- Misses       3381     3531     +150     

Impacted Files	Coverage Δ
...whisk/connector/kafka/KafkaConsumerConnector.scala	59.15% <ø> (-22.54%)	:arrow_down:
...whisk/connector/kafka/KafkaMessagingProvider.scala	70.73% <100.00%> (ø)
...whisk/connector/kafka/KafkaProducerConnector.scala	56.09% <100.00%> (-31.71%)	:arrow_down:

... and 29 files with indirect coverage changes

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