This changes the signature of InspectorSession.post_message to take a
&str rather than a String avoiding the need call str.to_string at each
call site.
This ports the REPL over to Rust and makes use of an inspector session to run a REPL on top of any isolate which lets make full use of rustylines various things like validators and completors without having to introduce a bunch of hard to test internal ops and glue code.
An accidental but good side effect of this is that the multiple line input we previously had is now an editable multi-line input prompt that is correctly stored in the history as a single entry.
To better reflect changes in error types in JS from #3662 this PR changes
default error type used in ops from "ErrBox" to "OpError".
"OpError" is a type that can be sent over to JSON; it has all
information needed to construct error in JavaScript. That
made "GetErrorKind" trait useless and so it was removed altogether.
To provide compatibility with previous use of "ErrBox" an implementation of
"From<ErrBox> for OpError" was added, however, it is an escape hatch and
ops implementors should strive to use "OpError" directly.
