Update example policy and documentation

[ConnorJC3]

What type of PR is this?

/kind documentation

What is this PR about? / Why do we need it?

This PR updates the example policy and associated documentation to be in sync with the upcoming managed policy revision.

In particular; it:

• Scopes down several permissions (notably changing * resources to specific types such as volume/* and snapshot/*)
• Adds necessary permission change for the upcoming CreateVolume IAM handling change
• Adds the EnableFSRs permission
• Reverts the previous change to use the * partition, instead choosing to document the partition name in install.md to be consistent with the managed policy
• Adds documentation around permissions for modifying tags (and cleans up the IAM section of install.md)

How was this change tested?

Manually/CI

Does this PR introduce a user-facing change?

Update the example IAM policy to be in sync with the AWS managed policy

[github-actions]

Code Coverage Diff

This PR does not change the code coverage

[ConnorJC3]

/hold

Going to sync this with release of the managed policy

[AndrewSirenko]

/lgtm

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AndrewSirenko

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