Implement simple device manager

[sz-po]

The goal of this task is to develop a solution that can initiate device processes, monitor their status, and terminate them as required. The device manager should have the following capabilities:

• Importing device specifications from the structure
• Starting the device process
• Detecting the process's end and restarting it if the exit-code is other than 0. If the error persists, an exponential backoff should be implemented.
• Triggering the end of the process by sending SIGTERM, waiting for a grace period, and then sending SIGKILL.

Furthermore, the structure describing the process should have a field that allows its value (also a structure) to be transferred as the device configuration. The configuration structure is unknown during compilation but should be passed as environment variables to the device process, prefixed with DKVMS_DEVICE_CONFIG_. For instance, the structure shown below expressed in YAML format:

display:
   id: foo

should be encoded as DKVMS_DEVICE_CONFIG_DISPLAY_ID.

Please ensure that appropriate information on how this mechanism works is provided in the readme.