Separate worker stacks and lock functions to one stack

[twelch]

This PR solves two issues:

• it solves the circular dependency issue in a better way. Instead of keeping worker lambdas in the same stack as their parent, it puts all workder lambdas instead into separate LambdaStacks, so you have two sets of stacks. This better supports more advanced use cases like two gp functions both using the same worker. When new functions get added to a project, they will fill out existing stacks before creating new ones.
• it locks gp functions to the first stack they get deployed to. This prevents deploy errors when functions move from one stack to another and CloudFormation isn't smart enough to delete the other Lambda first and claims a duplicate resource (because fixed lambdas ID). stack assignments are maintained between deploys in CfnOutput.