Hand off parse error to error checker if one is available

[gadenbuie]

1. Errors that happen when evaluating global_setup in evaluate_exercise() are now returned as internal errors
2. We no longer globally copy exercise.error.check.code into error_check, instead we do that operation when we actually go to evaluate the error checker. This lets us tell the difference between a global default option and an explicit error checker.
3. The parse error checker now runs the parse error through the error checker if one is available (and it's not the default error checker).

[rossellhayes]

Looks good to me!

[gadenbuie]

I added a few more changes that overhaul internal errors in learnr and to make sure that errors caused by exercise setup chunks aren't treated like user-generated errors:

• Internal error helper emits log messages via message() rlang::warn() and an error exercise result with specific internal (message) or external (feedback) facing language
• render_exercise() still catches setup and user code errors with the same tryCatch() block but returns an internal error if the error comes from the setup chunk(s)
• The error condition of internal errors is returned under $feedback$error
• When an error occurs and should be checked, we now pass the original user code error to the error checker, rather than the wrapped error we use to signal the issue
• We're now more careful about when we should be running the error checks

[rossellhayes]

Just to clarify f0c6366, warnings will show up in the console but not in the learnr exercise, correct?

[gadenbuie]

Just to clarify f0c6366, warnings will show up in the console but not in the learnr exercise, correct?

Yup, that's emitted either in the Shiny server or in the logs of the external evaluator