Distinguishing the PROD/EP_PROD/EP_OSKR and PROD_OSKR robots

## Issue Description
In order for any external software or client to provide support for all diferent types of the robots (resp. their firmwares - prod/ep-prod/oskr-prod/oskr-ep) and in order for such extenal software to offer different sets of features, it is needed to have the firmware(robot) distinguishable on the api protocol level (so it can be utilized through sdk's).

Right now, it seems that this is possible to be done only by distinguishing specific fimware version numbers, which is not a future-proof and stable solution for any extenral software/client of how to handle and recognize these different types of robots.

## Suggested Resolution
Implementing new flag to indicate the type of the robot, with:
- a new api [rpc external method](https://github.com/digital-dream-labs/vector-cloud/blob/main/internal/proto/external_interface/external_interface.pb.go#L72) that could be used for distinguising this flag specifically, or
- extending one of the existing rpc's to provide additioanl information of this flag (ie. [GetFeatureFlag](https://github.com/digital-dream-labs/vector-cloud/blob/main/internal/proto/external_interface/external_interface.pb.go#L233-L234), [VersionState](https://github.com/digital-dream-labs/vector-cloud/blob/main/internal/proto/external_interface/external_interface.pb.go#L171-L172)) (with backward compatibility in mind)