draft: implement bufferToString

[kiliczsh]

Trying to implement suggested performance improvement in nodejs/performance#16.

[mscdex]

Did you see the linked comment in the code comment for this function? I think we shouldn't be spending effort on optimizing APIs that exist solely for compatibility with older code.

[anonrig]

Did you see the linked comment in the code comment for this function? I think we shouldn't be spending effort on optimizing APIs that exist solely for compatibility with older code.

@mscdex This change also applies to several other places like _http_client.js and random.js (Referencing nodejs/performance#16)

[mscdex]

This change also applies to several other places like _http_client.js and random.js

That's fine, I'm referring specifically to btoa() (and atob() for that matter), which is what this PR is currently changing.

[kiliczsh]

It is not applicable anymore due to nodejs/performance#16