add private link parameters to data sync cmdlets

[ferno-ms]

Description

This is tied to the SDK change at Azure/azure-sdk-for-net#12179, and the design review at https://github.com/Azure/azure-powershell-cmdlet-review-pr/issues/596. I am submitting this in parallel before the previous ones get approved as this is a simple/localized change and we cannot really afford to wait for the next milestone.

This change adds a boolean UsePrivateLinkConnection parameter to the create and update commands for both sync groups and sync members, that indicates if the user wants sync groups to use private link connections. For the sync member case there is an extra resource ID that must be supplied to create the private link connection. Not supplying any of the new parameters keeps previous behavior.

Testing for the new behavior was done manually, as it requires manual setup. The old behavior is covered by existing tests.

Checklist

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• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • a cmdlet design review was approved for the changes in this repository (Microsoft internal only)
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