fix(metrics): image pull secrets for metrics collector

[swiatekm-sumo]

Ensure globally defined pull secrets are added to metrics collector ServiceAccounts. I've also added a test that checks all ServiceAccounts to ensure we catch this problem more easily in the future.

Fixes #3530

Checklist

• Changelog updated or skip changelog label added
• Documentation updated
• Template tests added for new features
• Integration tests added or modified for major features

[sumo-drosiek]

Do we need another serviceaccount for metrics. Can't we reuse the regular one? At this moment we have three serviceaccount:

• setup
• cleanup
• for installed chart

[swiatekm-sumo]

Do we need another serviceaccount for metrics. Can't we reuse the regular one? At this moment we have three serviceaccount:

* setup

* cleanup

* for installed chart

The metrics collector and target allocator have different required RBAC permissions, so they should have separate ServiceAccounts imo, based on the principle of least privilege. I think the same thing is true about setup and cleanup, which need to modify Secrets, unlike everything else.