[receiver/hostmetrics/memory] Add system.memory.usage{state=total}

[mx-psi]

Description:

Add system.memory.usage with state=total metric to report the total RAM memory available on the system.

After open-telemetry/semantic-conventions/pull/89 this is a valid value for system.memory.usage.

[songy23]

Tests are failing https://github.com/open-telemetry/opentelemetry-collector-contrib/actions/runs/6312718857/job/17139373415?pr=27096

[crobert-1]

Suggested change

	enum: [total, buffered, cached, inactive, free, slab_reclaimable, slab_unreclaimable, used]
	enum: [buffered, cached, free, inactive, slab_reclaimable, slab_unreclaimable, used, total]

This was almost in alphabetical order, we may as well sort all of it.

[crobert-1]

Tests are failing https://github.com/open-telemetry/opentelemetry-collector-contrib/actions/runs/6312718857/job/17139373415?pr=27096

Looks like the tests are relying on the index of datapoints within the gauge, and those are now off because of the new state.

[mx-psi]

After discussion with the semantic conventions WG we are going to change the spec for this first to

• prohibit total as a state value and
• ensure the sum of all dimensions corresponds to total