Signin and Signout redirect URIs are stored in committed source code and don't change with amplify env checkout calls

**Describe the bug**
Cognito signin and signout URIs are hard coded in backend auth cognito config. This causes merge conflicts when trying to merge branches with different environments and thus different values configured for the URIs.

**To Reproduce**
- create amplify project, new environment
- add auth, configure redirect URIs
- create a new environment
- configure different redirect URIs
- observe that redirect URIs are not stored as environment specific variables in team-provider-info.json but rather hard coded in amplify/backend/auth/cognito/parameters.json

**Expected behavior**
Values are stored as env specific vars in team-provider-info.json