Use the new audience field

[sima-zhu]

Use the new audience for service readme script.

For docs:

1. We use the APIs in release pipeline through Metadata-Helpers.ps1. (Fixed in this PR)
2. We use the API in docindex pipeline through Metadata-Helpers.ps1. (Fixed in this PR)

For notification:

1. We use the APIs from NotificationCreator through the GitHubToAADConverter

For pipeline owner extractor:

1. We use the APIs from pipeline-owners-extractor through the GitHubToAADConverter

Testing pipeline: https://dev.azure.com/azure-sdk/internal/_build/results?buildId=1993950&view=results

[azure-sdk]

The following pipelines have been queued for testing:
java - template
java - template - tests
js - template
net - template
net - template - tests
python - template
python - template - tests
You can sign off on the approval gate to test the release stage of each pipeline.
See eng/common workflow

[weshaggard]

I'm fine with this to fix the current issue but can you please file an issue to use our .NET tool similar to what we did in get-codeowners.ps1 script.

[ghost]

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