This commit removes all JS based text encoding / text decoding. Instead
encoding now happens in Rust via encoding_rs (already in tree). This
implementation retains stream support, but adds the last missing
encodings. We are incredibly close to 100% WPT on text encoding now.
This should reduce our baseline heap by quite a bit.
This commit marks the `Deno.Buffer` / `Deno.readAll` /
`Deno.readAllSync` / `Deno.writeAll` / `Deno.writeAllSync` utils as
deprecated, and schedules them for removal in Deno 2.0. These
utilities are implemented in pure JS, so should not be part of the
Deno namespace.
These utilities are now available in std/io/buffer and std/io/util:
https://github.com/denoland/deno_std/pull/808.
This additionallty removes all internal dependance on Deno.Buffer.
