Support extraEnv value setting for all flux controllers

[ravilr]

What this PR does / why we need it:

Add extraEnv helm value setting for all flux controllers. source-controller already has this. this change exposes the same across all controllers consistently. In case of using kubeconfig reference in HelmReleases or Kustomizations to reconcile on remote clusters, and in such setups where Kubernetes API endpoints of those remote clusters could require going through an egress proxy for reachability.

Checklist

• [x] DCO signed
• [x] Chart Version bumped
• [x] helm-docs are updated
• [x] Helm chart is tested
• [x] Update artifacthub.io/changes in Chart.yaml
• [x] Run make reviewable

[ravilr]

@stefanprodan @dwerder PTAL 🙏

[ravilr]

@stefanprodan if you don't mind closing above linked PRs and issues, which are all addressed by this PR. I missed linking the issue here. Thanks.

[bpinske]

While I appreciate this finally being merged upstream, I will admit it's a little irritating that my PR from 7 months ago which is near identical never went anywhere.