add support to deploy from local charms

[Felipe Reyes]

Add scripts to deploy using charms 2 years old (e.g. 18.05), these scripts should do something like this:

1) ./clone-all.sh --branch stable/18.05 --target /home/ubuntu/charms/

   Internally the script would do something like:

     cd $TARGET_DIR
     for CHARM in $LIST_OF_CHARMS; do
         git clone https://opendev.org/openstack/${CHARM}.git
         pushd $CHARM
         git checkout $BRANCH
         popd
     done

2) ./generate-bundle --charms-dir /home/ubuntu/charms/

    When --charms-dir is passed a new overlay is generated that contains lines like these:

    keystone:
      charm: /home/ubuntu/charms/keystone

[Edward Hope-Morley (hopem)]

Currently this can be achieved by doing generate-bundle without --run, modifying the bundles and overlays to use local copies and then re-running generate-bundle with --replay. A better solution would be to have something like a --charms-path option which if set will override all charms deployed. It would mean that you would have to always have all charms locally but if so then that should be easy enough. if the requirement is really to be able to deploy from a specific release then i think we should try to find a way to support that natively e.g. --charm-release 20.08 and then the generator goes and finds all the right versions (if they still exist).

[Edward Hope-Morley (hopem)]

moved to https://github.com/canonical/stsstack-bundles/issues/9