A processor that runs N pipeline branches concurrently.

System frames are broadcast to all branches. Data frames are sent to all branches (fan-out). Output from all branches is merged into the single downstream.

Usage in a pipeline:

pipeline = Feline.Pipeline.new([
  {SomeProcessor, []},
  {Feline.Pipeline.Parallel, branches: [
    [{BranchA1, opts}, {BranchA2, opts}],
    [{BranchB1, opts}, {BranchB2, opts}]
  ]},
  {AnotherProcessor, []}
])