Code button - separate CE and EE features

While working on Prepare common Vue app for Repository and Blob header area I realised that we have a Code button migrated to Vue already. But there's no separation of the EE features. We will need to create a parallel component inside ee/ directory and separate Kerberos related code there.

Migration MRs:

• Code dropdown: Migrate to GlDisclosureDropdown
• Code dropdown: Migrate to GlDisclosureDropdown (Part 2)

Vue Code button component:

• code_dropdown.vue