Delete database module

[gibizer]

The content of the module is moved to mariadb-operator/api module to avoid a circular dependency.

PR merging order:

• Copy the code to mariadb-operator
  - Move database module content from lib-common to /api mariadb-operator#156
• Adapt all the service operators to use the helpers from mariadb-operator instead of lib-common. Can be merged in parallel:
  • Use database helpers from mariadb-operator/api nova-operator#554
  • Use database helpers from mariadb-operator/api keystone-operator#323
  • Use database helpers from mariadb-operator/api placement-operator#88
  • Use database helpers from mariadb-operator/api glance-operator#333
  • Use database helpers from mariadb-operator/api neutron-operator#222
  • Use database helpers from mariadb-operator/api manila-operator#153
  • Use database helpers from mariadb-operator/api ironic-operator#343
  • Use database helpers from mariadb-operator/api heat-operator#254
  • Use database helpers from mariadb-operator/api cinder-operator#277
  • Use database helpers from mariadb-operator/api designate-operator#104
  • Use database helpers from mariadb-operator/api octavia-operator#182
  • Use database helpers from mariadb-operator/api barbican-operator#33
• Merge this PR to delete the unused database module from lib-common and therefore remove the mariadb dependency

[gibizer]

/hold

[stuggi]

/lgtm