Provides and caches session tokens used to authenticate eligible blob requests.

A SessionProvider owns the session cache and the machinery used to mint sessions. It can be shared across multiple clients (via SessionProvider) so that independently created clients reuse a single cache instead of each creating their own, avoiding redundant create-session requests.

This type has a closed hierarchy: it can be referenced but not derived from outside of the SDK. Use ContainerSessionProvider for token-credential based sessions.