Update Data Factory authentication to use managed identity to access Azure Files (airlock)

[SvenAelterman]

The Data Factory connector for Azure Files now supports using managed identities, including user-assigned managed identities (UAMI). The current implementation uses legacy shared key access with a connection string stored in Key Vault.

Doc ref: https://learn.microsoft.com/azure/data-factory/connector-azure-file-storage?tabs=data-factory#user-assigned-managed-identity-authentication

• Remove Azure Files connection strings from Key Vault.
• Update Azure File Shares authentication to allow the user-assigned managed identity for ADF to read and write files.
  • The UAMI needs the Storage File Data Privileged Contributor role
• Update the Linked Service definition for the generic File Share to use user-assigned managed identity.
• Remove the Key Vault Linked Service from ADF because it was only used to access the connection string secret.
• Turn off access key authentication on all storage accounts.

[SvenAelterman]

Implementing using the ADF's system-assigned identity for consistency with how blob storage is accessed. Tracking change to user-assigned managed identity in #214