Serviceaccount imagepullsecret support

[Pacobart]

Adding support for service accounts created with eks blueprint to use optional imagePullSecrets. This is needed due to some helm chart providers choosing to implement imagePullSecrets at the ServiceAccount object vs at the deployment/pod object(s). Cert-manager is one of these providers.

Motivation

• Resolves #

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Yes, I have added a new example under examples to support my PR
• Yes, I have created another PR for add-ons under add-ons repo (if applicable)
• Yes, I have updated the docs for this feature
• Yes, I ran pre-commit run -a with this PR

Note: Not all the PRs require a new example and/or doc page. In general:

• Use an existing example when possible to demonstrate a new addons usage
• A new docs page under docs/add-ons/* is required for new a new addon

For Moderators

• E2E Test successfully complete before merge?

Additional Notes

[Zvikan]

Let's make sure for next time to have an issue created and discussed first before working on a PR (following our contribution guidelines).

Minor doc comment, other than that LGTM, going to run TF plan workflow and then will approve it. Thank you