chore: bump Katib ROCKs version 0.15.0 -> 0.16.0-rc.1 for CKF release 1.8

[orfeas-k]

This PR updates Katib ROCKs for CKF release 1.8. Details in #31.
Bumped all ROCKs with following exceptions:

• cert-generator ROCK is completely removed since corresponding component
  was consolidated into katib-controller component Update Katib ROCKs to 0.16-rc.1 for CKF release 1.8 #31 (comment).
• katib-ui-rock needs to be rewritten since it is now based on wrong Dockerfile. Thus,
  no changes were introduced in this ROCK. katib-ui-rock is based on wrong Dockerfile #32
• katib-db-manager: Diverged from upsrteam by keeping binary for GRPC
  health checks

Fixes #31

Testing

Since there are no integration tests in place at the moment, the ROCKs were built and tested using the following commands (as instructed here in Basic Testing section)

export ROCK=<rockname without .rock>
sudo skopeo --insecure-policy copy oci-archive:${ROCK}.rock docker-daemon:${ROCK}:rock
docker run ${ROCK}:rock exec <service-command>
docker run ${ROCK}:rock exec pebble restart <service-name>
docker run ${ROCK}:rock exec pebble plan

[DnPlas]

Thanks @orfeas-k, this looks good, though I'd wait for @i-chvets' review just to confirm everything is alright.

[i-chvets]

One ROCK is missing from this update: https://github.com/canonical/katib-rocks/blob/kf-4177-update-katib-rocks-for-ckf-1.8/suggestion-goptuna/rockcraft.yaml suggestion-goptuna is already at correct version.

All other ROCKs built fine.

[i-chvets]

Approved.