allowEmptyResults but error on missing file

### What feature do you want to see added?

Currently the `allowEmptyResults: true` flag reports success when there are 0 tests in the junit file, or the junit file is missing.

We would like to be able to distinguish between when there are 0 tests in the junit file and when the junit file is missing.

This is important for tools like Trivy which generate test cases when they detect a vulnerability, but do not generate tests when no vulnerabilities are detected.

We want to distinguish between a junit file with 0 test cases and a missing junit file because this allows us to distinguish trivy running and finding 0 vulnerabilities and trivy failing and not generating a junit file.

We suggest adding a `disallowFileNotFound` flag which works in tandem with the `allowEmptyResults` flag to throw an error if the file is not found.

The documentation to generate a JUnit in Trivy is published here:
https://trivy.dev/v0.61/docs/configuration/reporting/#junit
The Jinja2 template used to generate the JUnit file is here:
https://github.com/aquasecurity/trivy/blob/main/contrib/junit.tpl

### Upstream changes

_No response_

### Are you interested in contributing this feature?

_No response_