Distinguish remote runtime directory and image directory

This commit refactors the code without changing the functionality.

A new argument, --remote-image-dir, will be added for remote host
cuttlefish. It will let the user separate images from the instance
files. The images can be reused for multiple acloud invocations.

Test: acloud-dev create -vv --local-image ~/target_files.zip \
      --cvd-host-package ~/cvd-host_package.tar.gz \
      --local-system-image ~/system.img \
      --host 192.168.9.2 --host-user vsoc-01 \
      --host-ssh-private-key-path ~/id_rsa
Bug: 293966645
Change-Id: I048612eeaffb0a2a7282aa82df38b53edac279ff
2 files changed