Convert to Codahale Metric interfaces where possible in WithMetricsSupport MetricRegistry

Currently in Spark runner all Beam metrics are reported by Codahale metrics as Codahale `Gauge` metrics.
Some of the metrics are formatted to look like their counterparts in Codahale's `GraphiteReporter` but this is a hack and should be avoided if possible.

Instead, convert Beam metrics to their Codahale counterparts in `WithMetricsSupport` getters where possible.

Since Beam metrics are not 100% compatible with Codahale metrics, consider where to make tradeoffs and stay with a simple `Gauge`.

Also, rename `WithMetricsSupport` something like `SparkBeamMetricRegistry`

Imported from Jira [BEAM-1692](https://issues.apache.org/jira/browse/BEAM-1692). Original Jira may contain additional context.
Reported by: aviemzur.

Start by locating WithMetricsSupport in the Spark runner and reading its MetricRegistry getters. Compare the Beam metrics exposed there with Codahale counterparts, identify which conversions are compatible and which should remain Gauges, and confirm whether the support class should be renamed; done means the agreed conversions and naming change are implemented without the current GraphiteReporter-formatting workaround.

Written by the indexing model from the issue text.