[prometheus-node-exporter] append extraArgs to default args

[harsh543]

Summary

• move the node-exporter filesystem ignore flags into a new defaultArgs value
• render container args with defaultArgs followed by user-provided extraArgs
• bump the prometheus-node-exporter chart patch version

Why

Previously, users adding one custom extraArgs entry had to copy the chart defaults as well or lose the default filesystem ignore rules. Keeping defaults in defaultArgs and appending extraArgs preserves the default behavior while making custom args additive.

Fixes #6831.

Validation

• /tmp/codex-helm/helm template pne charts/prometheus-node-exporter
• rendered with extraArgs: [--collector.textfile.directory=/run/prometheus] and confirmed default filesystem args are still present before the custom arg
• /tmp/codex-helm/helm lint charts/prometheus-node-exporter
• git diff --check

[harsh543]

Hey @jkroepke @zeritti @monotek 👋 — tagging you as the most active mergers on this repo.

What this does: Introduces defaultArgs — a new values key that prepends standard filesystem collector exclusion flags before extraArgs. The daemonset template uses concat (.Values.defaultArgs | default list) (.Values.extraArgs | default list) so both are always rendered in the correct order.

Why this matters: Right now users who want to customise extraArgs are forced to duplicate the default filesystem exclusion flags or lose them entirely. This is a footgun — omitting them causes node_exporter to attempt mounting /proc, /sys, /dev etc., which can block startup in restricted environments.

What's included:

• values.yaml: defaultArgs with the two standard filesystem exclusion flags; extraArgs stays empty by default
• daemonset.yaml: concat to merge both lists
• NOTES.txt: upgrade migration warning for users who previously set these flags via extraArgs
• unittests/daemonset_args_test.yaml: 4 helm-unittest cases covering default rendering, extraArgs appended, defaultArgs: [] opt-out, and opt-out + custom extraArgs

Upgrade safety: kingpin (used by node_exporter) uses the last value of a duplicate flag — no crash, no silent data loss. But the migration note in NOTES.txt gives users explicit guidance to clean up.

All helm lint --strict and helm template runs against the 9 CI values files pass clean. The helm unittest --strict suite runs 4/4 green.

Fixes #6831.

[monotek]

This changes the default and cant be a non major change.
I also don't think its worth it.