Add PSAzureSubscriptionPolicy for PSAzureSubScription.

[BethanyZhou]

Description

Common repo PR: Azure/azure-powershell-common#200

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)
  • the markdown help files have been regenerated using the commands listed here

[adxsdkps]

Can one of the admins verify this patch?

[BethanyZhou]

Hi Yeming, could you please help me review this PR? There is another PR needs to be reviewed first, Azure/azure-powershell-common#200 . Thanks.

[isra-fel]

Hi @BethanyZhou please see my inline comments.
Besides, PSAzureSubscriptionPolicy and the constructors of PSAzureSubscription need to be tested.
Thanks

[BethanyZhou]

Updated codes and removed local feeds. Please take a look. Thanks!

[isra-fel]

Very well!