Azure credentials update

[pavel-purma]

Update Azure Identity Credentials

• prefer AzurePipelineCredential if all environment variables are set
• cache initialization moved to DefaultIdentityTokenCredential so you can use only DefaultIdentityTokenCredential class with options and optionally disable short cache by DisableShortCache option
• Publish packages, blobs and symbols task set to use AzurePipelineCredential by adding SYSTEM_ACCESSTOKEN env value
• PublishArtifactsInManifestBase - use DefaultIdentityTokenCredential in symbols publishing

[mmitche]

@pavel-purma Still need this?

[mmitche]

How does the pipeline credential get access to publish blobs?

[pavel-purma]

It will use AzurePipelinesCredential when SYSTEM_ACCESSTOKEN environment variable provided. If not, ManagedIdentity/AzureCliCredential would be configured to ChainedTokenCredential

[pavel-purma]

@mmitche, this PR switches from DefaultAzureCredential to AzurePipelineCredential (DefaultIdentityTokenCredential standard pipeline authentication) which can issue tokens even after 10 minutes expiration issue of federated token. Authentication mechanism is also faster than in cases when DefaultAzureCredential falls to AzureCliCredential. In blob publishing this is already in use. Here, this code enables it also for symbols publishing.

[premun]

Suggested change

	var ret = new ChainedTokenCredential(tokenCredentials.ToArray());
	return ret;
	return new ChainedTokenCredential(tokenCredentials.ToArray());