Move Kleo group configs to gnupg home

The old entries will be copied to the new destination in
~/gnupg/kleopatra/kleopatragroupsrc, new entries are directly stored
there.

Test plan:

Tested with multiple conbination of:

• All groups are stored in ~/.config/kleopatragroupsrc
• Some groups are stored in ~/.config/kleopatragroupsrc, other are stored in ~/.gnupg/kleopatra/kleopatragroupsrc
• All groups are stored in ~/.gnupg/kleopatra/kleopatragroupsrc

In all cases, after starting Kleopatra, all groups were afterward stored
in ~/.gnupg/kleopatra/kleopatragroupsrc