[Internal] PPAF: Adds Code to Enable Read Hedging By Default

[kundadebdatta]

Pull Request Template

Description

This PR does the following two things:

• Enables Cross Regional Hedging by default with a threshold of either 1 second or half of the request timeout value provided, whichever is minimum, when PPAF is enabled. Note that the default availability strategy can be opted out by setting the AvailabilityStrategy to DisabledAvailabilityStrategy in the CosmosClientOptions. To understand this better, please take a look at the example below:

        CosmosClientOptions cosmosClientOptions = new CosmosClientOptions()
        {
            EnablePartitionLevelFailover = true,
            ConsistencyLevel = Cosmos.ConsistencyLevel.Strong,
            AvailabilityStrategy = new DisabledAvailabilityStrategy(),
        };
  

• As of today, during the cosmos client initialization, with PPAF enabled we ensure that either the ApplicationRegion or ApplicationPreferredRegions is present through a validation. Since we now have established the concept of Effective Preferred Region, this PR removes the above mandatory validation on ApplicationRegion or ApplicationPreferredRegions, as in the if there are no preferred regions passed explicitly, the .NET SDK can populate the effective preferred regions.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

Closing issues

To automatically close an issue: closes #5047, #5164

[github-actions]

All good!

[jeet1995]

LGTM - only ask from my side would be to double check how PPCB behaves with hedging on by default. In the Java SDK, we encountered a bug where PPCB doesn't kick in with hedging.