docs: More docs and improvements of existing docs

- Tried not to leave a single public function undocumented, though did not double-document public function with obvious names
- Remove all mentions of the strategy selector in favour of the strategy registry (to avoid confusion)

src/encoding/tycho_encoder.rs

@@ -4,6 +4,8 @@ use crate::encoding::{
     strategy_encoder::StrategyEncoderRegistry,
 };
 
+/// An encoder must implement this trait in order to encode a solution into a Transaction for
+/// execution using a Tycho router or related contracts.
 pub trait TychoEncoder<S: StrategyEncoderRegistry> {
     fn encode_router_calldata(
         &self,