Allow disabling additional suffixes in prometheus exporter

[dashpole]

Problem Statement

When migrating from OpenCensus to OpenTelemetry, and using Prometheus exporters, it causes a breaking change in the metric name for counters that were not complying with Prometheus naming recommendations. For example, the metric my.metric.foo became my_metric_foo in OpenCensus. But in OpenTelemetry, it now becomes my_metric_foo_total.

Proposed Solution

I would like an option to disable additional suffixes on the Prometheus exporter.

Alternatives

Force breaking changes on users who migrate from OpenCensus.

Additional Context

This is currently required by the prometheus specification: If the metric name for monotonic Sum metric points does not end in a suffix of _total a suffix of _total MUST be added, otherwise the name MUST remain unchanged.. I'm planning to address this in the specification.