[e2e] a11y reports are no longer being written to disk

[unlikelyzero]

Summary

After merging #7047 , I received a PR comment from @scottbell to

i think we should be using fs/promises here instead. Also, we shouldn't check for the file's existence before creating the directory as we could get into a race condition. something like this instead:

const fs = require('fs').promises;

async function writeAccessibilityReport(reportPath, accessibilityScanResults) {
    try {
        try {
            await fs.mkdir(TEST_RESULTS_DIR, { recursive: true });
        } catch (error) {
            if (error.code !== 'EEXIST') {
                throw error; // Throw the error if it is not because the directory already exists
            }
        }
        
        const data = JSON.stringify(accessibilityScanResults, null, 2);
        await fs.writeFile(reportPath, data); 
        console.log(`Accessibility report with violations saved successfully as ${reportPath}`);
        return accessibilityScanResults;
    } catch (err) {
        console.error(`Error writing the accessibility report to file ${reportPath}:`, err);
        throw err;
    }
}

This ticket tracks that work