Projects that seek to implement Node.js compatible APIs end up
needed to reproduce various bits of functionality internally in
order to faithfully replicate the Node.js behaviors. This is
particularly true for things like byte manipulation, base64 and
hex encoding, and other low-level operations. This change
proposes moving much of this low-level byte manipulation code
out of nodejs/src and into a new `nbytes` library. Initially this
new library will exist in the `deps` directory but the intent is
to spin out a new separate repository to be its home in the future.
Doing so will allow other projects to use the nbytes library with
exactly the same implementation as Node.js.

This commit moves only the byte swapping and legacy base64 handling
code. Additional commits will move additional byte manipulation
logic into the library.