[Feat]: Make system host labels first class citizens for node filtering

[ralphm]

Problem

System host labels are lumped in with user-provided labels and can only be filtered as keywords.

Description

System host labels are host labels that are dynamically created by the Agent and have a name that starts with an underscore (e.g. _cloud_instance_type). Most of these have values that are keywords, but others are booleans, numeric or have a magic value for "unknown" or "none".

Making proper facets out of these known labels could make filtering a lot more user friendly.

Importance

nice to have

Value proposition

1. More attractive rendering of known facets to filter on.
2. Better filtering options for non-keyword values
3. Possibility to include tooltips

Proposed implementation

### Suggested Changes
- [ ] Create human-readable display names for each system label (similar to facet display names in the Events tab)
- [ ] Add support for range filters for fields with numeric values (e.g. `_system_cpu_freq` or `_system_disk_space`.
- [ ] Add support for boolean values
- [ ] Handle "unknown" and "none" values consistently.
- [ ] Make the difference between Node
- [ ] Use a singular form for the all facet names (“Node” instead of “Nodes”).
- [ ] Possibly group facets and use icons just like the Node Info view.
- [ ] Make it clear that there is a difference between hostname and node name and why we have both.

### Additional facets for non-labels
- [ ] Replication factor
- [ ] Number of warnings/errors
- [ ] Enabled Features (health, ml)
- [ ] Node "roles"

Related tickets:

• #946
• #949