Add Support for I/O Metrics on macOS

[mbielak]

Description

With the infrastructure agent supported on macOS, when process samples are enabled it would be nice if the same set of metrics reported as they do across other OS variants. Specifically, on macOS in the ProcessSamples none of the I/O stats report to New Relic (I/O read bytes, I/O write bytes, I/O read count, I/O write count, I/O total read bytes, I/O total write bytes), other metrics do report in these samples.

Acceptance Criteria

This data is available per process sampled:
I/O read bytes
I/O write bytes
I/O read count
I/O write count
I/O total read bytes
I/O total write bytes

Describe Alternatives

Note in the docs we do not support this, and add a flex config to grab same metrics as an example.

Dependencies

unsure

Additional context

Estimates

For Maintainers Only or Hero Triaging this bug

Suggested Priority (P1,P2,P3,P4,P5):
Suggested T-Shirt size (S, M, L, XL, Unknown):

[workato-integration]

https://new-relic.atlassian.net/browse/NR-330966