"Fold m a b" vs "Parser a m b" type inconsistency

[harendra-kumar]

We made the parser type Parser a m b so that MonadTrans instance is possible. Although, we found that implementing local is not possible for Parser unless some changes are made to the type which may affect perf.

Now Fold and Parser are similar in nature and interconvertible but their types are inconsistent. We need to decide and keep it consistent across both.