[SQL] Add EndpointCertificate cmdlets

[ostojicb]

Description

This PR adds new cmdlet for getting endpoint certificates, along with some minor docs/comments fixes
Additionally we're bumping the SDK version again (followed by re-recorded tests)

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate ChangeLog.md file(s) has been updated:
  • For any service, the ChangeLog.md file can be found at src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md
  • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header -- no new version header should be added
• 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)
    • https://github.com/Azure/azure-powershell-cmdlet-review-pr/issues/1104
  • the markdown help files have been regenerated using the commands listed here

[wyunchi-ms]

/azp run azure-powershell - security-tools

[azure-pipelines]

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