Allow fairness weight overrides via UpdateTaskQueueConfig API (#626)

<!-- Describe what has changed in this PR -->
**What changed?**
+ Added two update fairness weight maps to the UpdateTaskQueueConfig api
request.
+ Added a fairness_weights map in the taskQueueConfig message to enable
persistence and return response.

<!-- Tell your future self why have you made these changes -->
**Why?**
+ Allow override of fairness weights for individual fairness keys via
UpdateTaskQueueConfig api.

<!-- Are there any breaking changes on binary or code level? -->
**Breaking changes**
+ No.

<!-- If this breaks the Server, please provide the Server PR to merge
right after this PR was merged. -->
**Server PR**

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Co-authored-by: Stephan Behnke <[email protected]>
Co-authored-by: Stephan Behnke <[email protected]>

Author: sivagirish81