Adds automatic population of unset retrypolicy field when starting Workflows

[mastermanu]

Change summary:

• Adds a separate dynamic configuration to dictate "default" retry policy field values for Workflows vs. Activities
• Adds logic to auto-populate unset retry policy fields for starting a workflow, signaling-to-starting a workflow, and starting a child workflow. If the specified retry policy is nil, no auto-population happens. If it is non-nil, unset fields are assigned defaults
• Fixes bug where WorkflowExpirationTime was always set to 0 for Child Workflows. This meant that Child Workflows would assume that max attempts = 0 implies no retry policy is set.
• Addresses flakiness in matching test (TestMatcherSuite/TestMustOfferRemoteMatch is flaky #243)

Validation:

• Added unit tests to ensure RetryPolicy is properly set for calls via FrontEnd
• Updated unit tests to validate ChildWorkflow is started with the correct WorkflowExpirationTime
• Validated using local application against one box environment

Backwards compatibility:

• For cases where the Retry Policy is set, but maximum attempts or other values were set to zero, we would not retry before. We will start retrying now. This is an edge case and broken behavior, so there is minimal risk here.

Future work:

• Remove setting of default Backoff Coefficient from GO SDK as the server now takes care of this completely.

[samarabbas]

Why is it called MaximumIntervalCoefficient? I think we should just call it MaximumInterval and use Duration as type.

[mastermanu]

We needed to initialize maximum interval in the case maximum interval was not set by the user, but a default maximum value might be less than the initial interval, which would then fail validation.

Btw, this change is already part of code-complete (this is just moving code around) and Maxim and I walked through this specific choice to use Coefficient vs. Interval before we landed this (it was initially an Interval).

Happy to discuss offline if we want to make further changes here though.

[samarabbas]

Overall looks good. You can land after addressing few minor comments.
It would be great if you can also add an integration test which covers default retry policies for activity and child workflows.