feat(cubestore): Add Azure Blob Storage support for remote filesystem

[tete17]

Issue Reference

Resolves #10332
Resolves #8288

Description of Changes Made

Add Azure Blob Storage as a remote filesystem backend for Cube Store, supporting multiple authentication methods:

• Account key: via CUBESTORE_AZURE_ACCESS_KEY
• SAS token: via CUBESTORE_AZURE_SAS_TOKEN
• DefaultAzureCredential: automatic fallback for workload identity, managed identity, and Azure CLI — no extra Cube Store env vars needed, uses standard AZURE_* variables

Implementation

• New AzureBlobRemoteFs struct implementing RemoteFs and ExtendedRemoteFs traits
• Uses the object_store crate (already a dependency) with the azure feature enabled
• FileStoreProvider::AzureBlob variant added to config with CUBESTORE_AZURE_CONTAINER and CUBESTORE_AZURE_ACCOUNT as required env vars
• No credential refresh loop needed — the azure_identity crate handles token lifecycle internally
• Telemetry instrumented with driver:azure_blob tags

Environment Variables

Variable	Required	Description
CUBESTORE_AZURE_CONTAINER	Yes	Blob container name (activates Azure backend)
CUBESTORE_AZURE_ACCOUNT	Yes	Storage account name
CUBESTORE_AZURE_ACCESS_KEY	No	Account access key
CUBESTORE_AZURE_SAS_TOKEN	No	SAS token
CUBESTORE_AZURE_SUB_PATH	No	Path prefix within the container
CUBESTORE_AZURE_ENDPOINT	No	Custom endpoint (Azurite, sovereign clouds)

Check List

• Tests have been run in packages where changes have been made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required