fix: Allows not setting optional attributes DataProcessRegion and CloudProviderConfig for FederatedDatabaseInstance

Proposed changes

Allows not setting optional attributes DataProcessRegion and CloudProviderConfig for FederatedDatabaseInstance

Link to any related issue(s): CLOUDP-219922

[x] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] This change requires a documentation update

[ ] I have signed the MongoDB CLA
[ ] I have added tests that prove my fix is effective or that my feature works
[ ] I have added any necessary documentation (if appropriate)
[ ] I have run make fmt and formatted my code
[ ] I have tested the CDK constructor in a CFN stack. See TESTING.md
[ ] If changes include removal or addition of 3rd party GitHub actions, I updated our internal document. Reach out to the APIx Integration slack channel to get access to the internal document.