[spacelift_stack_processor]: Add depends_on to Spacelift YAML stack config

[aknysh]

what

• [spacelift_stack_processor]: Add depends_on to Spacelift YAML stack config

why

• For each stack, in YAML stack config, allow specifying the stack dependencies on other components in the same environment and on other stacks
• Automatically detects if the dependency is a stack or a component in the current stack, and throws an error if it's not a valid stack and not a valid component
• depends-on then added to labels for the Spacelift stacks
• Will be used in Spacelift workflows (using Rego policies) to trigger the dependent stacks after the "parent" stacks finish running

test

    aurora-postgres-2:
      component: aurora-postgres
      settings:
        spacelift:
          workspace_enabled: true
          autodeploy: true
          labels:
            - "deps:config/secrets/dev-internal-secrets.yml"
          depends_on:
            - vpc
            - dns-delegated
            - gbl-dns-dns-primary

labels:
    - deps:stacks/catalog/rds-defaults.yaml
    - deps:stacks/globals.yaml
    - deps:stacks/uw2-dev.yaml
    - deps:stacks/uw2-globals.yaml
    - deps:config/secrets/dev-internal-secrets.yml
    - depends-on:uw2-dev-vpc
    - depends-on:uw2-dev-dns-delegated
    - depends-on:gbl-dns-dns-primary
    - folder:component/aurora-postgres-2
    - folder:uw2/dev

If any of the entries in depends_on is not a valid stack and not a valid component in the current stack, the following errors will be thrown:

Error: Component 'aurora-postgres-2' in stack 'uw2-dev' specifies 'depends_on' dependency 'vpc3', 
but 'vpc3' is not a stack and not a terraform component in 'uw2-dev' stack

Error: Component 'aurora-postgres-2' in stack 'uw2-dev' specifies 'depends_on' dependency 'gbl-ops-dns-primary', 
but 'gbl-ops-dns-primary' is not a stack and not a terraform component in 'uw2-dev' stack