Fix Cloud Run sample: canonical collector names, deploy command, service account

[seanbollin]

Fixes found via an end-to-end Cloud Run deploy test:

• Collector config: use canonical otelcol-google component names — rename the resourcedetection processor to resource_detection (the deprecated alias logs runtime warnings). The receiver stays otlp and the exporter stays otlp_grpc; those are already the canonical names for this distribution (there is no otlp_grpc receiver, and no plain otlp exporter). Verified with otelcol-google:0.156.0 validate (exit 0).
• Deploy command: drop the invalid --region flag from gcloud beta run worker-pools replace (region comes from the cloud.googleapis.com/location label in the YAML).
• Worker pool: add serviceAccountName: <SERVICE_ACCOUNT>, and document in the README that it needs roles/monitoring.metricWriter, roles/telemetry.tracesWriter, and roles/secretmanager.secretAccessor.
• Starter: drop the trailing ! from the workflow input so the result is Hello, Cloud Run Worker! (was Hello, Cloud Run Worker!!), matching the README.