Deprecate obsolete errors pkg

The /errors package has its origin in when capi providers were machineActuators that needed to vendor core capi to function.
There's no usage recommendations and value is questionable since we moved to CRDs and conditions for interoperability between core and providers.
I think we should deprecate it and if there's any use case relying on it we should support it via conditions

docs/book/src/developer/providers/migrations/v1.7-to-v1.8.md

@@ -33,3 +33,4 @@ maintainers of providers and consumers of our Go API.
 - To support Kubernetes 1.31, providers should stop setting caBundle to invalid values in there CRDs (see core CAPI PR: https://github.com/kubernetes-sigs/cluster-api/pull/10972)
   Setting caBundle to `Cg==` is a pattern that is widely spread across the ecosystem but it will stop working with Kubernetes 1.31.
   Please see the following Slack thread for details: https://kubernetes.slack.com/archives/C0EG7JC6T/p1722441161968339
+- The Errors package [has been deprecated in v1.8](https://github.com/kubernetes-sigs/cluster-api/issues/10784). It's recommented to remove any usage of the currently exported variables.

errors/doc.go

@@ -15,4 +15,6 @@ limitations under the License.
 */
 
 // Package errors makes a set of error message handlers available for use by Cluster API Providers.
+//
+// Deprecated: This package will be removed in one of the next releases.
 package errors