* remove immutable

* add fallback function to deposit eth into l2

* Revert "remove immutable"

This reverts commit 6e8bf7b1871b56085ce96ee73b5acbd4bd04b96c.

* remove conflicting receive function
Co-authored-by: George Hotz <geohot@gmail.com>
Co-authored-by: smartcontracts <kelvinfichter@gmail.com>