`ScreenBeamProfileMeasurement` Fails if `beam_fit` != `ImageProjectionFit`

[electronsandstuff]

Describe the bug
ScreenBeamProfileMeasurement.fit_data(...) assumes image fit results have attribute signal_to_noise_ratio which isn't defined in parent class. See lcls_tools/common/measurements/screen_profile.py ln 155.

        for image in processed_images:
            fit_result = self.beam_fit.fit_image(image)
            rms_sizes_all.append(np.array(fit_result.rms_size))
            centroids_all.append(np.array(fit_result.centroid))
            total_intensities_all.append(fit_result.total_intensity)
            signal_to_noise_ratios_all.append(fit_result.signal_to_noise_ratio)

signal_to_noise_ratio is defined in ImageProjectionFitResult, but not the generic ImageFitResult which will cause errors if people use the code for image fitting methods other than ImageProjectionFit.