feat: add support for ETag option in res.sendFile (#6073)

This patch introduces the ability to control the ETag generation
through the `res.sendFile` function. Specifically, the ETag option
is wired to the application's configuration, allowing it to be
enabled or disabled based on the app's settings.

Fixes: https://github.com/expressjs/express/issues/2294

Signed-off-by: Juan José Arboleda <soyjuanarbol@gmail.com>