monitoring: fix hardware Grafana dashboard and health metrics

monitoring: fix hardware Grafana dashboard and health metrics

- Fix fan repeating panels: set multi=true on fan_speeds template
  variable so Grafana generates one panel per fan instead of one
- Remove TACH-only regex filter on fan_speeds template and AVG
  Cooling query so all system fans are visible regardless of naming
- Replace duplicate Power Control panel with Network health panel
- Fix NVMe drive count to use storage_capacity_bytes{protocol=NVMe}
  instead of counting temperature sensors (inaccurate proxy)
- Normalize all hostname filters to regex match (=~) for consistency
- Register hardware.libsonnet in dashboards.libsonnet so the
  dashboard JSON is generated during ceph-mixin builds
- Add temperatures category to prometheus health metrics loop

Signed-off-by: Afreen Misbah <afreen@ibm.com>
Assisted-by: Claude
Signed-off-by: Afreen Misbah <afreen@ibm.com>
(cherry picked from commit 04207ca6dcfc86c51845912848d9cbf1a7cb87d0)