Align example READMEs and fix kafka-connector on OpenShift

[gfinocchiaro]

Align example READMEs and fix kafka-connector on OpenShift

Cleans up and aligns the three example READMEs on a common structure, and fixes a few issues that blocked the kafka-connector example on OpenShift.

kafka-connector

• Made the apache/kafka image work under OpenShift's restricted-v2 SCC by backing /opt/kafka/config/ and /opt/kafka/logs/ with emptyDir volumes — no anyuid grant needed.
• Consolidated everything into a single lightstreamer namespace (previously split across kafka + lightstreamer with broken DNS).
• Rewrote the OpenShift producer build to use oc new-build --dockerfile=... (inline Dockerfile).
• Removed steps that require project-create/delete rights, so the workflow runs on shared or admin-provisioned projects.

All three READMEs

• Moved the "namespace must exist beforehand" requirement into Prerequisites.
• Unified section layout, bullet pattern, and Cleanup wording.
• Merged Verify the deployment into each install step; promoted Accessing the web client to a top-level section in the adapter READMEs.

Files

• examples/kafka-connector/README.md
• examples/kafka-connector/kafka.yaml
• examples/kafka-connector/producer.yaml
• examples/in-process-adapters/README.md
• examples/proxy-adapters/README.md