Update to ACK runtime v0.56.0, code-generator v0.56.0 (#17)

### Update to ACK runtime `v0.56.0`, code-generator `v0.56.0`

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* ACK code-generator `v0.56.0` [release notes](https://github.com/aws-controllers-k8s/code-generator/releases/tag/v0.56.0)
* ACK runtime `v0.56.0` [release notes](https://github.com/aws-controllers-k8s/runtime/releases/tag/v0.56.0)

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NOTE:
This PR increments the release version of service controller from `v0.2.2` to `v0.3.0`

Once this PR is merged, release `v0.3.0` will be automatically created for `opensearchserverless-controller`

**Please close this PR, if you do not want the new patch release for `opensearchserverless-controller`**

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#### stdout for `make build-controller`:

```
building ack-generate ... ok.
==== building opensearchserverless-controller ====
Copying common custom resource definitions into opensearchserverless
Building Kubernetes API objects for opensearchserverless
Generating deepcopy code for opensearchserverless
Generating custom resource definitions for opensearchserverless
Building service controller for opensearchserverless
Running GO mod tidy
Generating RBAC manifests for opensearchserverless
Running gofmt against generated code for opensearchserverless
Updating additional GitHub repository maintenance files
==== building opensearchserverless-controller release artifacts ====
Building release artifacts for opensearchserverless-v0.3.0
Generating common custom resource definitions
Generating custom resource definitions for opensearchserverless
Generating RBAC manifests for opensearchserverless
```

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Author: ack-bot

.github/workflows/postsubmit.yaml

@@ -0,0 +1,10 @@
+name: Hydrate Go Proxy
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  call-hydrate-go-proxy:
+    uses: aws-controllers-k8s/.github/.github/workflows/reusable-postsubmit.yaml@main