First version of DataDog (#15218)

[msJinLei]

• Fix for output type and null subscriptions collection in ResourceGraph (Fix for output type and null subscriptions collection in ResourceGraph #15135)

• Fixed null subscriptions exception, added change log

• Added output type fix and updated tests
  Changes from PR avoid breaking customer experience #15125

• regenerated ps1xml, updated examples

• Updated md file for the output type and changelog

• added breaking change issues csv after rebasing with master

• added parenthesses to csv to fix parsing issue

Co-authored-by: makharch makharch@microsoft.com

• Move DataDog to master

• Add DataDog to documentation/azure-powershell-modules.md

• Add SignatureIssues.csv for skip static analysis pipeline.

Co-authored-by: fenwickt 69487545+fenwickt@users.noreply.github.com
Co-authored-by: makharch makharch@microsoft.com
Co-authored-by: azurepowershell azurepowershell@ms.com
Co-authored-by: wyunchi-ms yunwang@microsoft.com

Description

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)
    • {Please put the link here}
  • the markdown help files have been regenerated using the commands listed here