feat(host_metrics source): Implement process collection for host metrics

[LeeTeng2001]

Summary

Implement process metric collection for host metrics souce

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

A simplistic vector config for testing, additionally, it has unit test written in similar style to other host metrics

[sources.host]
type = "host_metrics"
collectors = ["process"]

[sinks.my_sink_id]
type = "console"
encoding.codec = "json"
inputs = ["host"]

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Please read our Vector contributor resources.
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
  run dd-rust-license-tool write to regenerate the license inventory and commit the changes (if any). More details here.

References

#9626

[bits-bot]

All committers have signed the CLA.

[pront]

Thanks @LeeTeng2001! There a few failing CI checks. cargo fmt should fix them.

See how to run common checks locally here: https://github.com/vectordotdev/vector/blob/master/CONTRIBUTING.md#running-other-checks