Fix #385, adds generic driver interface and Linux sysmon module

[jphickey]

Checklist (Please check before submitting)

• [x] I reviewed the Contributing Guide.
• [x] I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution Defines an "iodriver" interface with a simple module id + opcode + argument interface, which can be extended as necessary for different purposes.

Also adds a "linux_sysmon" module that implements this interface to provide system monitoring capabilities. This includes, but is not limited to, the CPU utilization that HS needs.

Fixes #385

Testing performed Build and run CFE with (patched) HS, observe CPU utilization getting reported correctly via the PSP module

Expected behavior changes Adds "iodriver" pluggable/extendable interface, and "linux_sysmon" for health monitoring

System(s) tested on Debian

Contributor Info - All information REQUIRED for consideration of pull request Joseph Hickey, Vantage Systems, Inc.

[jphickey]

@dzbaker all issues have been cleaned up now, should be good to go.