Nsgs feature

[vladcristi]

What this PR does / why we need it:
This PR adds support to bring your own VCN and subnets outside of Cluster API, but still use Cluster API to provision and manage NSG.

Which issue(s) this PR fixes:
Fixes #418

[dranicu]

Unit tests:

[opc@capoci-env cluster-api-provider-oci]$ make test
GOBIN=/home/opc/git/cluster-api-provider-oci/hack/tools/bin ./scripts/go_install.sh sigs.k8s.io/controller-runtime/tools/setup-envtest setup-envtest v0.0.0-20230131074648-f5014c077fc3
kube-builder assets: /home/opc/.local/share/kubebuilder-envtest/k8s/1.24.2-linux-amd64
KUBEBUILDER_ASSETS="/home/opc/.local/share/kubebuilder-envtest/k8s/1.24.2-linux-amd64" go test -coverprofile=coverage.out ./... 
        github.com/oracle/cluster-api-provider-oci              coverage: 0.0% of statements
ok      github.com/oracle/cluster-api-provider-oci/api/v1beta1  38.486s coverage: 23.1% of statements
        github.com/oracle/cluster-api-provider-oci/cloud/config         coverage: 0.0% of statements
        github.com/oracle/cluster-api-provider-oci/cloud/metrics                coverage: 0.0% of statements
ok      github.com/oracle/cluster-api-provider-oci/api/v1beta2  0.033s  coverage: 14.5% of statements
ok      github.com/oracle/cluster-api-provider-oci/cloud/ociutil        0.008s  coverage: 15.9% of statements
        github.com/oracle/cluster-api-provider-oci/cloud/scope/mocks            coverage: 0.0% of statements
        github.com/oracle/cluster-api-provider-oci/cloud/services/base          coverage: 0.0% of statements
        github.com/oracle/cluster-api-provider-oci/cloud/services/base/mock_base                coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/services/compute       [no test files]
        github.com/oracle/cluster-api-provider-oci/cloud/services/compute/mock_compute          coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/services/computemanagement     [no test files]
        github.com/oracle/cluster-api-provider-oci/cloud/services/computemanagement/mock_computemanagement              coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/services/containerengine       [no test files]
        github.com/oracle/cluster-api-provider-oci/cloud/services/containerengine/mock_containerengine          coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/services/identity      [no test files]
        github.com/oracle/cluster-api-provider-oci/cloud/services/identity/mock_identity                coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/services/loadbalancer  [no test files]
        github.com/oracle/cluster-api-provider-oci/cloud/services/loadbalancer/mock_lb          coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/services/networkloadbalancer   [no test files]
        github.com/oracle/cluster-api-provider-oci/cloud/services/networkloadbalancer/mock_nlb          coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/services/vcn   [no test files]
        github.com/oracle/cluster-api-provider-oci/cloud/services/vcn/mock_vcn          coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/services/workrequests  [no test files]
        github.com/oracle/cluster-api-provider-oci/cloud/services/workrequests/mock_workrequests                coverage: 0.0% of statements
ok      github.com/oracle/cluster-api-provider-oci/cloud/scope  19.647s coverage: 75.6% of statements
ok      github.com/oracle/cluster-api-provider-oci/cloud/util   0.090s  coverage: 61.1% of statements
ok      github.com/oracle/cluster-api-provider-oci/controllers  1.825s  coverage: 59.2% of statements
ok      github.com/oracle/cluster-api-provider-oci/exp/api/v1beta1      11.196s coverage: 15.3% of statements
ok      github.com/oracle/cluster-api-provider-oci/exp/api/v1beta2      0.033s  coverage: 4.8% of statements
        github.com/oracle/cluster-api-provider-oci/feature              coverage: 0.0% of statements
?       github.com/oracle/cluster-api-provider-oci/version      [no test files]
ok      github.com/oracle/cluster-api-provider-oci/exp/controllers      0.488s  coverage: 56.3% of statements
go tool cover -func=coverage.out -o coverage.txt
go tool cover -html=coverage.out -o coverage.html

E2E Results:

Ran 9 of 31 Specs in 2883.792 seconds
SUCCESS! -- 9 Passed | 0 Failed | 0 Pending | 22 Skipped