[AZI-62] Make partition count configurable in log forwarder automation

[iotmani]

What does this PR do?

Make partition count configurable in log forwarder automation.
Useful for adding more control to scaling the event hub as needed.

Motivation

AZI-62

Testing Guidelines

I deployed the parent template, with Event Hub partitionCount set to 28, and I could see it deployed correctly:

Additional Notes

Docs:
https://docs.microsoft.com/en-us/azure/templates/microsoft.eventhub/namespaces/eventhubs?tabs=json

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)
• This PR passes the unit tests
• This PR passes the installation tests (ask a Datadog member to run the tests)

[ashwingandhi-ddog]

@iotmani I think you went over this in the demo, but why do we need this change in parent_template.json as well when its in event_hub.json ?

[iotmani]

@iotmani I think you went over this in the demo, but why do we need this change in parent_template.json as well when its in event_hub.json ?

The event_hub.json is what deploys the eventhub and can technically be deployed independently if so desired.
The parent_template.json is the entry point for all resources/templates we want customers to be able to tweak, hence to allow them to override the default we'd need to expose another parameter there also, otherwise it would default to 32.

Think of it as just passing parameter x to function foo, which subsequently needs to call function bar. (and we don't have the ability to pass all kwargs like in Python :) ).