[Storage] Support HDFS feature and web endpoint in Account properties

[blueww]

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Add HDFS feature and web endpoint support to Storage Account.

Already pass review in private repo in PR:
https://github.com/Azure/azure-rest-api-specs-pr/pull/507
https://github.com/Azure/azure-rest-api-specs-pr/pull/504

Changes include:

• Add web endpoint
• Add dfs endpoint
• Add Account property IsHndEnabled
• Change the example subscription to {subscription-id} per suggestion in DocumentDB API Status? #504

Rest doc: https://microsoft.sharepoint.com/teams/AzureStorage/_layouts/15/Doc.aspx?sourcedoc=%7B00d45481-7f25-4170-a95e-82dbc6a3041d%7D&action=default&slrid=0d385f9e-a0fa-0000-758b-e5dde88dbd09

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• If applicable, the PR references the bug/issue that it fixes.
• Swagger files are correctly named (e.g. the api-version in the path should match the api-version in the spec).

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