Fixes#3663
In JSON mode, `opa check -b` collapsed all compilation errors into one
opaque string, unlike non-bundle mode which lists each with its code and
location. The bundle loader wraps errors as `fmt.Errorf("bundle %s: %w",
...)`, and NewOutputErrors default case stringified the wrapper instead
of the structured ast.Errors inside it.
The default case now unwraps and recurses, keeping the wrapper's message
only when unwrapping reveals nothing structured.
Signed-off-by: Sebastian Spaink <sebastianspaink@gmail.com>
Sebastian Spaink
31065f123e