This adds an implementation of `Default` for both `WorkerOptions` and
`BootstrapOptions`. Since both of these structs are rather big, this
should make it easier for people unfamiliar with the internals to focus
on the options relevant to them.
As a user of `deno_runtime` I feel like these should serve as good
defaults, getting people them started without having to tweak the
runtime. Additionally even if some changes are made, the usage of
`..Default::default()` will significantly help with code clarity and
verbosity.
The following transformations gradually faced by "JsError" have all been
moved up front to "JsError::from_v8_exception()":
- finding the first non-"deno:" source line;
- moving "JsError::script_resource_name" etc. into the first error stack
in case of syntax errors;
- source mapping "JsError::script_resource_name" etc. when wrapping
the error even though the frame locations are source mapped earlier;
- removing "JsError::{script_resource_name,line_number,start_column,end_column}"
entirely in favour of "js_error.frames.get(0)".
We also no longer pass a js-side callback to "core/02_error.js" from cli.
I avoided doing this on previous occasions because the source map lookups
were in an awkward place.
