Copy scripts in batch and add executability with rsync

[martinhoyer]

Copying scripts one by one is not efficient and take quite some time, we could do just one guest.push instead of multiple, see tmt/steps/execute/init.py:

        with script as source:
            for dest in [script.path, *script.aliases]:

Additionally, we could implement --executability or --perms, --chmod rsync options instead of running chmod command.