OPA doesn't consider built-in error fatal, but Conftest does. Can we revert the change?

[ruokai-lai]

Request:
OPA doesn't consider built-in error fatal, but Conftest does. Can we revert the change? Or make it print out builtin errors as opa with flag --show-builtin-errors.

In OPA, where it shows "built in errors are not fatal":
Run opa eval --help: you can see --show-builtin-errors collect and return all encountered built-in errors, built in errors are not fatal.

In Conftest, where it shows conftest fails with built in error:
introduced in version 0.42 https://github.com/open-policy-agent/conftest/blob/master/policy/engine.go#L449

if len(*builtInErrors) > 0 {
		return output.QueryResult{}, fmt.Errorf("built-in error: %s", (*builtInErrors))
}

Example of failure:
this will fail my conftest: https://play.openpolicyagent.org/p/wyU6iLcazl
and this will not fail my conftest: https://play.openpolicyagent.org/p/uk0FOQyNsO

[boranx]

I think it's fair to expect to have a similar user experience to OPA for builtin errors
to address that, I've moved the builtin errors behind a flag (--show-builtin-errors) in the PR: #871