feat: add loginConfig to source/dest, handle in caller

[scanlonp]

Features added:

• Adds LoginConfig interface and LoginType enum.
• LoginConfig is now a required property in SourceConfig and DestinationConfig.
• Source/Destination now generate docker login commands.
• Added logic to determine if the codebuild job needs to logout and login to a different registry.
• Added documentation detailing that the current Source.ecr and Destination.ecr functions only cover the scope of ECR repositories in the same account as the stack
  • a different function + class will be needed for 'external' ECR repositories

Changes:

• Setup of Destination. Now bind() returns the destinationConfig.