The current implementation of op_encoding_encode_into UTF-8 encodes each
individual code point in the input string into the output buffer. But after the
ops binding, the input is a Rust String, so the UTF-8 bytes can simply be copied
to the output. This should improve this API's performance.
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.
