Suggest obvious fix when action id includes type

[adpaco-aws]

Description of changes

This PR extends the validation of action IDs so that we detect cases in which the user may have mistakenly included the entity type (i.e., "Action::") in the action ID. In that case, we don't suggest another action ID like we used to, but instead draw attention to the fact that the action ID was defined with the entity type in its name. This avoids misleading the user when the fix is much simpler.

Resolves #166

Checklist for requesting a review

The change in this PR is (choose one, and delete the other options):

• A bug fix or other functionality change requiring a patch to cedar-policy.

I confirm that this PR (choose one, and delete the other options):

• Does not update the CHANGELOG because my change does not significantly impact released code.

I confirm that cedar-spec (choose one, and delete the other options):

• Does not require updates because my change does not impact the Cedar formal model or DRT infrastructure.

I confirm that docs.cedarpolicy.com (choose one, and delete the other options):

• Does not require updates because my change does not impact the Cedar language specification.

[john-h-kastner-aws]

Looks pretty good.

[john-h-kastner-aws]

IMO worth adding an line in the changelog. We weren't consistent with mentioning error message changes like this leading up to the 4.0 release since we had made a ton of error message tweaks, but I like including these small improvements.

[cdisselkoen]

Looks good overall.