[FEATURE] Composite blocks should support the same pipeline syntax as pipelines

[rhazn]

User Story

1. As a {user}
2. I want {to split my pipelines in composite blocks}
3. So that {I can organize my code better}

User Acceptance Criteria

• Split pipelines / multiple pipelines are possible in composite blocks, see Composite blocktypes: Basic functionality #411 (comment)

Definitions of Done

• A PR has been opened and accepted
• All user acceptance criteria are met
• All tests are passing

[georg-schwarz]

We should consider the verbose syntax as well. Or generally remove the verbose syntax of pipes?

[rhazn]

I think we should just get rid of it, I don't really see the point anymore, no?