AsyncCacheNonBlocking - Improve availability during replica movement

[aayush3011]

Description

The current AsyncCache on force refreshes removes the value. It then creates a new value and all incoming requests are stuck waiting for the new task to complete.

Issue
If a single replica moves only 1 of the 4 replicas URIs is stale. The current async cache is blocking all requests until the value is updated. The 3 other replicas could be used to successfully complete requests.

Solution
AsyncCacheNonBlocking was created. This async cache does not block requests on refresh. It instead returns the stale value until the refresh is complete. Then the refresh value is used to update the cache. Any request using the forceRefresh to true will wait on the same refresh task.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.
• Benchmark Tests
• Benchmark Tests:

Benchmark Workload in Prod on West US 2 during upgrades

Workload Test RU: 100,000 Documents: 100,000 Time Duration: 60 hrs Region: West US 2*

Throughput - Mean Rate

Throughput - m5 Rate

Latency - p95

Latency - p99

Latency - p999

Latency - max

Benchmark Test RU: 100,000, Documents: 100,000, Region: South Central US**

Throughput:

P95 Latency

P99 Latency

P999 Latency

Max Latency

[aayush3011]

/azp run java - cosmos - tests

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[aayush3011]

/azp run java - cosmos - tests

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[aayush3011]

/azp run java - cosmos - tests

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[aayush3011]

/azp run java - cosmos - tests

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[FabianMeiswinkel]

LGTM - except for few NITs aroung logging and isDebugEnabled check

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