Don't attempt to "guess sourcemap reference" for bundles #2503
Description
When uploading bundles via sentry-cli sourcemaps upload, the bundle sourcemap path is directly passed to the command (--bundle-sourcemap is required when --bundle is provided). Therefore, we should not be calling guess_sourcemap_reference in the code path for unpacking the bundle. Instead, we should use the path provided, and error if no sourcemap is present at that path.
Making this refactor likely will allow the tests to pass on the parent issue's PR.