Unit tests: state tracking

This issue is to keep track of unit tests related to state tracking (read/write to local and omap states).
- [ ] Test if local state dict is as expected after adding bdev
- [ ] Test if local state dict is as expected after removing bdev
- [ ] Test if local state dict is as expected after adding subsystem
- [ ] Test if local state dict is empty after adding all subsystem-related components (subsystem, namespace, host, & listener) and then removing the subsystem
- [ ] Test if delete_state resets contents of local state dict
- [ ] Test if local state dict is as expected after adding listener
- [ ] Test if local state dict is as expected after removing listener
- [ ] Test if local state dict is as expected after adding host
- [ ] Test if local state dict is as expected after removing host
- [ ] Test if local state dict is as expected after adding namespace
- [ ] Test if local state dict is as expected after removing namespace
- [ ] Test if omap is as expected after add_bdev (version number and omap contents)
- [ ] Test if omap is as expected after remove_bdev (version number and omap contents)
- [ ] Test if omap is as expected after add_subsystem (version number and omap contents)
- [ ] Test if omap is as expected after after adding all subsystem-related components (subsystem, namespace, host, & listener) and then remove_subsystem
- [ ] Test if omap is as expected after add_namespace (version number and omap contents)
- [ ] Test if omap is as expected after remove_namespace (version number and omap contents)
- [ ] Test if omap is as expected after add_host (version number and omap contents)
- [ ] Test if omap is as expected after remove_host (version number and omap contents)
- [ ] Test if omap is as expected after add_listener (version number and omap contents)
- [ ] Test if omap is as expected after remove_listener (version number and omap contents)
- [ ] Test if omap is empty after deleting contents

Start by locating the local state dictionary, omap handling, and the add/remove entry points named in the checklist: bdev, subsystem, namespace, host, listener, and delete_state. Add unit tests covering each listed operation, including version numbers and cleanup; done means every checklist item passes and both state stores are empty when expected.

Written by the indexing model from the issue text.