Use PLAYWRIGHT_DRIVER_PATH environment variable as driver cache directory

[GuyGoldenberg]

Playwright uses PLAYWRIGHT_BROWSERS_PATH to define the cache directory used to install the browsers.
See playwright implementation - link

  const envDefined = getFromENV('PLAYWRIGHT_BROWSERS_PATH');
  if (envDefined === '0') {
    result = path.join(__dirname, '..', '..', '..', '.local-browsers');
  } else if (envDefined) {
    result = envDefined;
  } else {
    let cacheDirectory: string;
    if (process.platform === 'linux')
      cacheDirectory = process.env.XDG_CACHE_HOME || path.join(os.homedir(), '.cache');
    else if (process.platform === 'darwin')
      cacheDirectory = path.join(os.homedir(), 'Library', 'Caches');
    else if (process.platform === 'win32')
      cacheDirectory = process.env.LOCALAPPDATA || path.join(os.homedir(), 'AppData', 'Local');
    else
      throw new Error('Unsupported platform: ' + process.platform);
    result = path.join(cacheDirectory, 'ms-playwright');
  }

[canstand]

@GuyGoldenberg The Playwright driver directory is used for clients only. And PLAYWRIGHT_BROWSERS_PATH has a significantly different intent. That's why I prefer to add the PLAYWRIGHT_DRIVER_PATH environment variable.

[mxschmitt]

nit: I'd probably put it into into the first line of getDefaultCacheDirectory, then the caller side is simpler. Either the user given value or our internal logic.

[canstand]

I put it in transformRunOptions and added some comments. getDefaultCacheDirectory still maintains its single purpose.

Users can now understand the usage through the type comments of RunOptions.