maint: [network-agent] fix up network-agent chart

[JamieDanielson]

Which problem is this PR solving?

Failed release because Chart name (hny-network-agent) didn't match directory name (network-agent).

Short description of the changes

• We opted for network-agent for chart name because honeycomb and/or honeycombio will be included when using the chart. The dataset names and container/pod names are intentionally kept as hny-network-agent to make it more easily distinguishable since these are things the user will see in a running k8s cluster.
• Added the environment variables necessary for the use of k8s downward API in the agent, which adds k8s metadata to events so the agent knows things about itself.

How to verify that this has the expected result

Events have all expected k8s metadata... and the release works 😅 😅

[robbkidd]

But hold up, we're going to try this locally.

[robbkidd]

Tested locally. Hangs together. 🦖 🌮 👍🏻