outputs.groundwork: adding properties for metric

[ymkins]

Feature Request

The GroundWork output plugin supports limited data subset of a metric.

Proposal:

Improve parsing to process more data form metric fields and tags
as output payload data-structure allows more specific data.

Current behavior:

No options to set output LastPluginOutput.
No options to set output service properties.
Thresholds are processed from "critical" and "warning" tags only.

Desired behavior:

Process "message" field and tag for LastPluginOutput value.
Fields and tags that has suffix "_cr"/"_wn" should be processed as critical and warning thresholds
for specific field in addition to "critical" and "warning" tags.
Unknown tags should be used to set output service properties.

Use case:

Using more data from input plugins.
In work on integrating solution with syslog input it allows handle more data
from inputs such as severity level.