Write screenshot to file

[negiDharmendra]

• Changed default screenshot grabber to write to file and return file path.
• Depricate existing custom screenshot grabber API contract.
• Create a new API contact for custom screenshot grabber to write the screenshot into file and returning file path instead of screenhsot bytes.

const path = require("path");
const { screenshot } = require('taiko');
gauge.customScreenshotWriter = async function () {
    const screenshotFilePath = path.join(process.env['gauge_screenshots_dir'], 'screenshot.png');
    await screenshot({ path: screenshotFilePath });
    return path.basename(screenshotFilePath);
};