🐛 Remove GetPolicy IAM call when attaching to role

[adammw]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Alternative solution to #5265 that uses principle of least privilege by removing the need for iam:GetPolicy entirely. If the policy doesn't exist, assume that the AttachPolicy call will fail rather than attempting to fetch it before attachment.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #5254

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• includes emojis
• adds unit tests
• adds or updates e2e tests

Release note:

Remove GetPolicy IAM call when attaching to role

[k8s-ci-robot]

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[richardcase]

/ok-to-test