Add an Azure Blob Storage backend to Arctic

Add an Azure Blob Storage backend to Arctic: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Arctic can currently be pointed at S3 ( s3:// / s3s:// ) and LMDB ( lmdb:// ) backends. We want to add Azure Blob Storage as a first-class backend so that users can point…

The task

`Arctic` can currently be pointed at S3 (`s3://` / `s3s://`) and LMDB (`lmdb://`) backends. We want to add **Azure Blob Storage** as a first-class backend so that users can point `Arctic` at an Azure storage account using an `azure://` connection URI, exactly the way S3 and LMDB are wired in today.

Part of FineEnvs/MiMo-V2.6-RL-harbor-code.