Retire Cookie core class override

[clpetersonucf]

When SameSite cookie requirements first became an issue, FuelPHP did not yet support those headers appropriately out of the box. They are now supported within the core Cookie class, which makes our override copy of the class more or less obsolete. It could potentially be a liability as additions are made to the core class that are not reflected in our own copy.

It should be reasonable to retire our copy of the Cookie class in favor of the one in fuel/core and add the required configs to set the SameSite=None and Secure=true cookie headers.