fix(iam): incorrect input for AccountPrincipal is building successfully

[duranbe]

Reason for this change

There is no validation and test that the AWS Account Id when creating AccountPrincipal Object. In my case I missed a digit when copy pasting an account id and the build still passed, the typo has been caught only during the code review process

Description of changes

Adding simple regex to check that AWS Id is 12 digits long & update error message

Description of how you validated changes

• Update existing tests
• Add 2 units ones

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

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[aws-cdk-automation]

Your pull request must be based off of a branch in a personal account (not an organization owned account, and not the main branch). You must also have the setting enabled that allows the CDK team to push changes to your branch (this setting is enabled by default for personal accounts, and cannot be enabled for organization owned accounts). The reason for this is that our automation needs to synchronize your branch with our main after it has been approved, and we cannot do that if we cannot push to your branch.

[aws-cdk-automation]

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❌ Fixes must contain a change to an integration test file and the resulting snapshot.
❌ Pull requests from `main` branch of a fork cannot be accepted. Please reopen this contribution from another branch on your fork. For more information, see https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md#step-4-pull-request.

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[aws-cdk-automation]

Your pull request must be based off of a branch in a personal account (not an organization owned account, and not the main branch). You must also have the setting enabled that allows the CDK team to push changes to your branch (this setting is enabled by default for personal accounts, and cannot be enabled for organization owned accounts). The reason for this is that our automation needs to synchronize your branch with our main after it has been approved, and we cannot do that if we cannot push to your branch.

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 63b0423
• Result: FAILED
• Build Logs (available for 30 days)

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