feat: include all envs in gen 2 data codegen

[dpilch]

Description of changes

Add table mappings for all envs to Gen 2 Codegen.

import { defineData } from \"@aws-amplify/backend\";
export const data = defineData({
    // Replace each environment name with the corresponding branch name. Use \"sandbox\" for your sandbox environment.
    importedAmplifyDynamoDBTableMap: {
       prod: { Todo: 'todo-table-prod' },
       staging: { Todo: 'todo-table-staging' },
       /**
        * Unable to find the table mapping for this environment.
        * This could be due the enableGen2Migration feature flag not being set to true for this environment.
        * Please enable the feature flag and push the backend resources.
        * If you are not planning to migrate this environment, you can remove this key.
        */
        dev: {}
    },
    schema: \"TODO: Add your existing graphql schema here\"
});

Issue #, if available

N/A

Description of how you validated changes

Unit tests

Checklist

• PR description included
• yarn test passes
• Tests are changed or added

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