Move EOI to Parser companion object

Improve Parser cursor manipulations

Remove unnecessary import of opTreeCtx

Remove unnecessary `c.universe`
Move `PartialFunction[Tree, OpTree]` to `type FromTree[T <: OpTree]`
Remove unnecessary `PartialFunction` creation
Eliminate `EOI` expression by moving it to LiteralChar
Extend `OpTree` from `OpTreeCompanion`
Speed up `LiteralString` reify
Add `TODO` to improve `Sequence` expression model in future
Replace `show` with `Decoded`
Update `object ParserInput`