Provide node labels with metadata

[htroisi]

Is your feature request related to a problem? Please describe.
It would be useful to be able to aggregate telemetry data by node label. For example, node label metadata could be used to identify interzonal traffic, as requested in this issue.

Describe the solution you'd like
Provide node labels (as a string) along with the existing metadata.

Additional context

• For anyone interested in implementing this, you can see how Pod labels were added to Pixie's metadata in this PR: Add capability to get pod labels #468
• You can also find a description of how to add to Pixie's metadata here: Provide pod labels with metadata #449 (comment)

[Sush-Dew]

@htroisi Could you assign this issue to me? I am a beginner and this issue seems a good first issue to resolve.

[htroisi]

Hi @Sush-Dew! I think that @victor-timofei might be working on this feature already. Do any of the other Pixie issues tagged with the "good first issues" label look interesting to you?

[htroisi]

@victor-timofei were you able to get the dev environment running? If not, let us know and we'd be happy to help unblock you.

[shardulsrivastava]

@htroisi if this issue is available, I can work on this