fix: add special macie principal in opt-in regions

[allcloud-sahar-hagbi]

For supporting opt-in regions, we need to add to the centralized s3 bucket KMS key resource-based policy, the following principal: "macie.{opt-in-region}.amazonaws.com". This grants permission to the KMS key to take actions on the s3 bucket content within an opt-in region.

The code I've added is pretty much straight forward, so I don't feel a need to elaborate on it.
Thx in advance.

[erwaxler]

Hey @allcloud-sahar-hagbi , thank you for your code submission! The team has reviewed this change and incorporated it into the code base, this will be available in our next major release. Thank you for supporting the Landing Zone Accelerator on AWS!