Add database readscale related properties support

[bradrich-msft]

Description

• Added SecondaryType to the following:
  • New-AzSqlDatabase
  • Set-AzSqlDatabase
  • New-AzSqlDatabaseSecondary
• Added HighAvailabilityReplicaCount to the following:
  • New-AzSqlDatabase
  • Set-AzSqlDatabase
• Removed ReadReplicaCount from the following:
  • New-AzSqlDatabase
  • Set-AzSqlDatabase

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)
    • No new cmdlets added
  • the markdown help files have been regenerated using the commands listed here

[msJinLei]

@bradrich-msft
Have you finished a cmdlet review here https://github.com/Azure/azure-powershell-cmdlet-review-pr/issues?
Your PR cannot contains break changes for a non major release

[bradrich-msft]

@msJinLei thank you for your comment. The breaking change has already been completed in APIs and SDKs and released worldwide. We need the powershell cmdlets to be updated so as not to cause customer blockers. Please advise on how we can get this reviewed and approved or otherwise when will the next major release take place? Thanks again.

[bradrich-msft]

@msJinLei I have added back the removed property and marked as deprecated per instructions. This is no longer a breaking change. Please review. Thank you.

[msJinLei]

/azp run

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