[FEATURE] AzureUploader: Support SAS urls

[coonmoo]

Problem

Egress AzureUploader only supports accountname / shared key authentication.
Shared keys grant the Livekit Azure uploader excessive permissions like listing/reading all files in the account.

If the shared key would be compromised all recordings in the blob storage account would be exposed.
We are concerned with having the shared key being passed to Livekit Cloud's egress environment where we don't have any control.

Solution

Support Azure Blob Storage container SAS urls in AzureUploader.
This would allow us to use authentication with write only permissions for the storage container.

[davidzhao]

I would encourage you to submit a PR for the feature if you are interested.