[cgroupruntime] add extension to contrib builder manifest (#39202)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

Adds the cgroupruntime extension to the builder manifest so it can be
added to the k8s and contrib distributions.

<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
#37201

<!--Describe what testing was performed and which tests were added.-->
#### Testing

<!--Describe the documentation added.-->
#### Documentation

<!--Please delete paragraphs that you did not use before submitting.-->

---------

Co-authored-by: Antoine Toulme <[email protected]>

Author: rogercoll

cmd/otelcontribcol/builder-config.yaml

@@ -54,6 +54,7 @@ extensions:
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/encoding/zipkinencodingextension v0.123.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/encoding/skywalkingencodingextension v0.123.0
   - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/k8sleaderelector v0.123.0
+  - gomod: github.com/open-telemetry/opentelemetry-collector-contrib/extension/cgroupruntimeextension v0.123.0
 
 exporters:
   - gomod: go.opentelemetry.io/collector/exporter/debugexporter v0.123.0