Storage test infra refactor

[jaschrep-msft]

Pulls some basics of client tests out of XxxTestBase hierarchy and into separate utility classes so they can be accessed outside of said hierarchy. Useful for writing unified tests across multiple Storage services without excessive code duplication.

Key Changes:

• TenantConfigurationBuilder houses code previously in StorageTestBase that grabs TenantConfigurations out of a config file.
• ClientBuilder houses genericized code previously in BlobTestBase/DataLakeTestBase/etc. that creates XxxServiceClients out of results from TenantConfigurationBuilder.
• Each service test suite has a ClientBuilderExtensions class that decorates the ClientBuilder with functionality that doesn't fit easy into generics.

Notes to reviewers:

• This is not intended to be a comprehensive change covering all facets of test infra. It is a starting point that will lead towards better maintenance and immediately open some doors for current testing needs.
• Currently, these separated classes are still dependent on some functionality provided by Azure Core's RecordedTestBase, and so we still have to pass in an instance of that. We need access to the Recording management and InstrumentClient. Not ideal but still a significant improvement.

[kasobol-msft]

very nice, this is going into right direction.