Adds key ``theme_src_archive`` to ``horizon_custom_themes``,
which should point to archive with packed theme inside.
Archive should be placed on the deployment host and it
may be easily created by git-archive, or ansible git module.
Structure inside archive should be as a standard theme,
without any leading folders.
Unarchive is used instead of synchronize with flat files,
as synchronize establishes independent SSH connection
and doesn't use nspawn or any other methods from
custom ssh plugin and may case connection errors.
Recursive copy has limitations on number of files inside of the
directory. This limit is pretty high, but still it's a limit.
This method differs from uploading custom files, as themes may
have complex structure and include a lot of files.
As a result, if ``horizon_custom_themes`` contains
``theme_src_archive`` key, theme will be distributed by role.
Change-Id: Icbfff0793a703de94091cfdcdecf5a2c91bae4be
Related-Bug: 1778098
acf7a29609