ci: enable github workflow

Failed on focal install hook because:

$ juju exec --unit juju-backup-all/0 --wait 50s ./hooks/install
Traceback (most recent call last):
  File "./src/charm.py", line 15, in <module>
    from utils import JujuBackupAllHelper
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/src/utils.py", line 18, in <module>
    from jujubackupall.process import BackupProcessor
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/jujubackupall/process.py", line 24, in <module>
    from juju.application import Application
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/juju/application.py", line 9, in <module>
    from . import model, tag, utils, jasyncio
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/juju/model.py", line 25, in <module>
    from . import provisioner, tag, utils, jasyncio
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/juju/provisioner.py", line 11, in <module>
    import paramiko
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/paramiko/__init__.py", line 22, in <module>
    from paramiko.transport import SecurityOptions, Transport
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/paramiko/transport.py", line 91, in <module>
    from paramiko.dsskey import DSSKey
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/paramiko/dsskey.py", line 37, in <module>
    from paramiko.pkey import PKey
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/paramiko/pkey.py", line 31, in <module>
    import bcrypt
  File "/var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/bcrypt/__init__.py", line 13, in <module>
    from ._bcrypt import (
ImportError: /var/lib/juju/agents/unit-juju-backup-all-0/charm/venv/bcrypt/_bcrypt.abi3.so: undefined symbol: PyCMethod_New

The jammy functional test seems working well, so it's not a runner issue.

canonical / charm-juju-backup-all

ci: enable github workflow #21