CosmosClientBuilder APIs and Docs

[kushagraThapar]

• Improve description of CosmosClientBuilder -> Current form: Helper class to buildAsyncClient CosmosAsyncClient instances as logical representation of the Azure Cosmos database service.

Improvements:

• Build both async client and sync client.

• Build examples.

• Description to the class - add mandatory fields - key and endpoint

• Default to directMode - without the need for the API.

• Add two examples -
  ** one with just mandatory params and consistency level
  ** one with some customization (consistencyLevel, directModeConfig, preferredRegions, multipleWriteRegionsEnabled)

• Add comment on consistency level - that it is optional but customer should pay attention

• buildAsyncClient() - update docs to match buildClient()

• Update multipleWriteRegionsEnabled documentation to default to true.

[kushagraThapar]

This is done.