migration fails to complete on oci

[Caner Derici]

`juju migrate` with juju 2.9 on OCI is able to transfer a model, but is stuck before teardown with an `AdoptResources not implemented (not implemented)` error, seemingly originated from:

https://github.com/juju/juju/blob/a07b91749f22b1c505fdc709b13e9196bd11b041/provider/oci/environ.go#L325

This seems to be happening on only the OCI, other providers should be fine.

Here's some extra info:

$ juju bootstrap --config compartment-id=$OCID_COMPARTMENT oci-canonical test-controller1
$ juju bootstrap --config compartment-id=$OCID_COMPARTMENT oci-canonical test-controller2
$ juju switch test-controller1
$ juju add-model --config compartment-id=$OCID_COMPARTMENT test-model
$ juju deploy ubuntu

Then after everything's active

$ juju migrate test-model test-controller2

Then on the new controller the model becomes active, however you should see that the old one is stuck with something similar to the following:

Model Controller Cloud/Region Version SLA Timestamp Notes
test-model test-controller1 oci-canonical/us-phoenix-1 2.9.24.1 unsupported 14:43:20-07:00 migrating: transferring ownership of cloud resources to target controller

App Version Status Scale Charm Store Channel Rev OS Message
ubuntu 20.04 active 0/1 ubuntu charmhub stable 19 ubuntu

Unit Workload Agent Machine Public address Ports Message
ubuntu/0 unknown lost 0 158.101.43.146 agent lost, see 'juju show-status-log ubuntu/0'

Machine State DNS Inst id Series AZ Message
0 down 158.101.43.146 ...7rwwyq focal running