feat(iconv): implement iconv and encodings : ASCII, (unicode defined encodings)utf8, utf16, utf32

[rishadbaniya]

Instead of following a dynamic library loading method(which GNU does) we have gone for static library(since we have small set of encodings right now), this adds on less complexity for dev purpose as well,

FYI: we can always move to a dynamic library approach in the future if we need...as the encoding follows the following flow

FROM ENCODING -> UCS-4 FORMAT(Intermediate format in our case) -> TO ENCODING

[jgarzik]

Main comment is about a non-streaming implementation. Is streaming easy or difficult?

For the user, reading everything into memory is a challenge for very large files.

[rishadbaniya]

i've replaced with chain of iterator consumption(with a circular buffer of max size 10000 bytes)..hence large files will work with very low memory footprint

i.e streaming has been enabled