Delete create_*_src and revert_*_src tasks and replace with Deploy options

[jlantz]

Replace with dynamic functionality via a task option on the deploy task. The following tasks should be deleted along with their task classes:

• create_managed_src
• create_unmanaged_ee_src
• revert_managed_src
• revert_unmanaged_ee_src

The logic should be added to the Deploy task class for dynamic injection using the following options:

• managed_src: Injects the equivalent of create_managed_src
• unmanaged_ee_src: Injects the equivalent of revert_unmanaged_ee_src

Once this is done, there should no longer be any instances where default CumulusCI flows rely on the persistence of files modified by a prior task. It will also streamline working with deployment errors in the ci_master and unmanaged_ee flows.