Memory leak in unused metric label feature

[winder]

Subject of the issue

There is a dynamic "label" feature in Gauge and StringGauge. The label is a string argument when collecting metrics used as a key into the gauge dataset. If we ever use the feature for something unbound like round, address or session ID. At that point memory would grow unbounded until a crash.

A couple of possible solutions (we would need to do this for both gauges):

1. Remove the labels feature (it seems to only be used by segment.go:EnterSegment and that function is not called anywhere).
2. Return from this function immediately when len(valueIndices) <= 1
3. Set maxMetricRetensionDuration to something very large in config.json

Earlier discussion here: #2508 (comment)

Acceptance criteria

Remove labels that can be associated with metrics.
Why: using the labels may lead to memory issues that lead to the node crashing.

Priority

Low / Tech debt

[iansuvak]

Started working on this with approach 1 and noticed that Counters also support labels and that unlike Gauges they do use the labels for networkConnectionsDroppedTotal in wsNetwork.go so if the same memory leak concern applies there as well the simple solution of removing labels functionality won't work.

Should we deal with both of them at the same time or limit this issue to just Gauge struct which would further decrease parity between the two?