🔥 feat: Add support for graceful shutdown timeout in ListenConfig (#3220)

* 🔥 feat: Add support for graceful shutdown timeout in Listen

* 📚 doc: update the description of GracefulShutdownTimeout

* ♻️refact: use require.ErrorIs instead of require.Equal

* fix: Target error should be in err chain by using fasthttputil.ErrInmemoryListenerClosed

* ♻️refact: use require.ErrorIs instead of require.Equal

* 📚doc: update the description of GracefulShutdownTimeout

* ♻️refact: rename GracefulShutdownTimeout to ShutdownTimeout

* 🩹fix: set default ShutdownTimeout to 10s

---------

Co-authored-by: Juan Calderon-Perez <835733+gaby@users.noreply.github.com>