Replace internal metrics with Micrometer

[robfrank]

ArcadeDB has an internal metric/monitorinfg component and a http endpoint that provides some data in a custom format.

The idea is to replace the component using Micrometer (https://micrometer.io/) to gather internal metrics, adding more meters (counter, gauge, etc.) where necessary and provide standard ways to connect to monitoring services: prometheus, graphite, etc.

• remove the internal metric component
• add micrometer and replace previous meter
• for back compatibility map new metrics to old names/values on the http endpoint
• implement a Prometheus ServerPlugin as the first integration point
• add documentation covering configuration and integration with external tools

[gramian]

I would appreciate Prometheus via this way for metrics via HTTP.

[lvca]

Back compatibility is not super important (never documented), but Studio: the metrics should show up there.

[gramian]

And the JMX metrics are for development only, right?