Add an option to protected branches to add writing deploy keys to the whitelist for pushing.

Please note this is technically a breaking change: previously if the owner of a repository was on the whitelist then any writing deploy key was effectively on the whitelist. This option will now need to be set if that is desired.

Closes #8472 

Details:
* Allow Protected Branches to Whitelist Deploy Keys
* Add migration
* Ensure that IsDeployKey is set to false on the http pushes
* add not null default false