[tmpnet] Move monitoring label handling to node

[maru-ava]

PR Chain: tmpnet+kube

This PR chain enables tmpnet to deploy temporary networks to Kubernetes. Early PRs refactor tmpnet to support the addition in #3615 of a new tmpnet node runtime for kube.

• [tmpnet] s/Network.ChainConfigs/Network.PrimaryChainConfigs/ #3854
• [tmpnet] Provide genesis, subnet and chain config via content flags #3857
• [tmpnet] Ensure Node has a reference to Network #3870
• [tmpnet] Switch back to using maps for subnet config #3877
• [tmpnet] Refactor runtime configuration in preparation for kube #3867
• [tmpnet] Unify start network flag usage between e2e and tmpnetctl #3871
• [tmpnet] Avoid serializing the node data directory #3881
• [tmpnet] Rename NodeProcess to ProcessRuntime #3890
• [tmpnet] Switch FlagsMap from map[string]any to map[string]string #3884
• [tmpnet] Ensure tmpnet methods always have a logger #3893
• [tmpnet] Ensure all node runtime methods accept a context #3894
• [tmpnet] Move WaitForHealthy from a function to a tmpnet.Node method #3896
• [tmpnet] Delegate writing of the flag file to the runtime #3897
• >>>>>> [tmpnet] Move monitoring label handling to node #3898 <<<<<<
• [tmpnet] Enable runtime-specific restart behavior #3882
• [tmpnet] Enable deployment to kube #3615
• [tmpnet] Enable monitoring of local kind cluster #3794

Why this should be merged

Previously, determination of labels to apply to collected logs and metrics was the responsibility of the process runtime. Since these labels are common to both runtimes, it makes sense for the node to own it.

How this was tested

CI

Need to be documented in RELEASES.md?

N/A

TODO

• Merge parent [tmpnet] Delegate writing of the flag file to the runtime #3897

[Copilot]

Pull Request Overview

This PR centralizes the handling of monitoring labels by moving the logic from the process runtime to the node, ensuring that both log and metric collection use the same label source.

• Removed inline monitoring label generation from process_runtime.go
• Introduced getMonitoringLabels() in node.go to encapsulate label determination
• Updated check_monitoring.go to use environment variables directly for GitHub labels selectors

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tests/fixture/tmpnet/process_runtime.go	Removed explicit label mapping; now calls getMonitoringLabels()
tests/fixture/tmpnet/node.go	Added getMonitoringLabels() and a global githubLabels variable for label names
tests/fixture/tmpnet/check_monitoring.go	Revised fallback logic to retrieve GitHub labels directly from environment variables