Add various streaming transducers

[satabin]

• [x] Copyless Streaming Tree Transducers which can be used to implement query languages over tree like data
• [x] Streaming Finite State Transducers which can be used for matching inputs and emitting some output
• [x] ~Streaming String Transducers which can be used for matching inputs and emitting some output as soon as possible~

[satabin]

I decided to merge this PR without support for SST because:

• STT can be used to implement features that are independent from SST (e.g. query languages)
• SST require a lot more work to be functional I will also add documentation (and probably some reworks and improvements) when implementing the higher level features on top of these transducers.