Rename "toFold" from the Parser module to unsafeToFold

[harendra-kumar]

This is a partial function as folds are less powerful than parsers, not all parsers can be safely converted to folds. However, folds converted to parsers can be safely converted back to folds.

[adithyaov]

Should we expose unsafeToFold I use it quite often when dealing with parsers.

[adithyaov]

The use of word unsafe is not required here. This is a partial function, just like head. Making all partial functions unsafe , removes the credibility of the unsafe keyword.