Support mixing images in local-image-local-instance mode

Acloud supports mixing local cuttlefish images with the system image
given by --local-system-image. Mixing the images requires OTA tools and
misc info of cuttlefish build. Acloud gets them from either environment
variables or command line arguments. The developers can use this feature
to test locally built images and the artifacts downloaded from build

Test: acloud-dev create --local-instance \
      --local-image --local-system-image
Test: acloud-dev create --local-instance \
      --local-image ~/aosp_cf_x86_phone-target_files \
      --local-system-image ~/aosp_x86-img \
      --local-tool ~/cvd-host_package \
      --local-tool ~/otatools
Bug: 176270532
Change-Id: I516848ce847178041b976cc65dea4aa342202a11
6 files changed