Add supervisor state reading interface

[gemenerik]

Currently, the library does not provide direct access to the supervisor states, making it difficult to determine whether the drone is considered landed or flying. In the client, we work around this by performing a bitfield check on the supervisor states which we parse from log data, but having this functionality built into the library would make it much easier to use.

The lack of direct supervisor state access complicates certain behaviors, such as detecting when the drone has landed. For example: Right now, we must continuously send zero setpoints until we can safely assume the drone landed, since stopping setpoints prematurely can trigger a supervisor intervention. If the library exposed the supervisor states directly, we could make better-informed decisions based on the actual supervisor status.