mgr/prometheus: refactor hardware metrics

mgr/prometheus: refactor hardware metrics

- export `firmware_version` labels from `node_proxy_storage_capacity_bytes` metrics to be used in device firmware panel
- improve iterations for performance - dropping redundant node_proxy_firmware() RPC; firmware data is already
  present in the fullreport response, and removing unnecessary loops.
- replace health if/elif chain with HEALTH_STATUS_MAP dict lookup
- rename metrics to ceph_hardware_*, fix component labels and add tests
- added unit test cases
- add serial name, slot info to capacity metric
- fix health metrics showing ID instead of component name

Signed-off-by: Afreen Misbah <afreen@ibm.com>