feat: Add cluster name check for ocicluster webhook

[joekr]

What this PR does / why we need it:
This will now check the cluster name before trying to create. We had some issues where the cluster would fail to come up due to networking issues if the cluster had a . in the name.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #142

[joekr]

e2e

Ran 5 of 22 Specs in 2125.467 seconds
SUCCESS! -- 5 Passed | 0 Failed | 0 Pending | 17 Skipped

unit tests

?       github.com/oracle/cluster-api-provider-oci      [no test files]
ok      github.com/oracle/cluster-api-provider-oci/api/v1beta1  1.503s  coverage: 19.4% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/config [no test files]
ok      github.com/oracle/cluster-api-provider-oci/cloud/ociutil        0.667s  coverage: 25.0% of statements
ok      github.com/oracle/cluster-api-provider-oci/cloud/scope  167.689s        coverage: 72.9% of statements
?       github.com/oracle/cluster-api-provider-oci/cloud/scope/mocks    [no test files]
?       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  [no test files]
?       github.com/oracle/cluster-api-provider-oci/cloud/services/computemanagement     [no test files]
?       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        [no test files]
?       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  [no test files]
?       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  [no test files]
ok      github.com/oracle/cluster-api-provider-oci/controllers  27.981s coverage: 71.0% of statements
?       github.com/oracle/cluster-api-provider-oci/exp/api/v1beta1      [no test files]
?       github.com/oracle/cluster-api-provider-oci/exp/controllers      [no test files]
?       github.com/oracle/cluster-api-provider-oci/feature      [no test files]
?       github.com/oracle/cluster-api-provider-oci/version      [no test files]