Allow non-Double Gauges

[erikd]

Currently using Prometheus Gauges to log a Word64 using fromIntegral and it gets reported as:

db_slot_height  2.3628703e7

This is a little suboptimal.

Would it be worth adding a Word64 gauge? If you can point me in the direction of what you want, I may even find time to do it myself.

[wraithm]

I think that's a great idea. Feel free to add it! Word64Gauge?

[brandonchinn178]

Would it make sense to generalize as Gauge a? Not sure about the internal details, but just from the public API, it seems trivial to allow Gauge to contain any numeric value

[brandonchinn178]

FYI I have a prototype making Gauge and Counter polymorphic:

• Gauge
• Counter