[Storage] Support Storage Account failover

[blueww]

Description

The feature target to release on 10/15. Since the time limitation, send PR directly to public repo. Please help to review it ASAP.

Swagger PR (in review) : Azure/azure-rest-api-specs#4107

Rest Spec :
Failover: https://microsoft.sharepoint.com/:w:/r/teams/AzureStorage/_layouts/15/Doc.aspx?sourcedoc=%7B77CFF0F4-AFAD-4AC1-B51C-1F17C92E06AF%7D&file=SRP%20Customer-controlled%20failover%20API.docx&action=default&mobileredirect=true
Get Last Sync Time：https://microsoft.sharepoint.com/:w:/r/teams/AzureStorage/_layouts/15/doc2.aspx?sourcedoc=%7bad30891d-7c70-4d4f-9b95-046d40fa900d%7d&action=edit&wdPid=660b6155

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• Please add REST spec PR link to the SDK PR
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[dsgouda]

@blueww I see the REST spec PR is waiting on ARM review. The initial PR looks good but I would wait on the spec to be merged before approving

[dsgouda]

@blueww could you open a new PR when the spec is ready? I can review it again