Add Cloud Run for GCP CI env

[roger2hk]

Towards #42 #53

There will be another pull request for the Cloud Build and Artifact Registry.

Logs from Cloud Run:

DEFAULT 2024-11-18T20:23:54.842230Z I1118 20:23:54.842376 1 main.go:90] **** CT HTTP Server Starting ****
INFO 2024-11-18T20:23:55.592629Z STARTUP TCP probe succeeded after 1 attempt for container "conformance" on port 6962.
INFO 2024-11-18T20:23:55.730635Z [protoPayload.serviceName: run.googleapis.com] [protoPayload.methodName: /Services.CreateService] [protoPayload.resourceName: namespaces/transparency-dev-playground/revisions/ci-static-ct-00001-9lm] Ready condition status changed to True for Revision ci-static-ct-00001-9lm.
DEFAULT 2024-11-18T20:23:56.603144Z I1118 20:23:56.604538 1 gcp.go:580] Consuming from 0
DEFAULT 2024-11-18T20:23:56.609708Z I1118 20:23:56.611167 1 gcp.go:618] Found no rows to sequence
INFO 2024-11-18T20:23:57.017163Z [protoPayload.serviceName: run.googleapis.com] [protoPayload.methodName: /Services.CreateService] [protoPayload.resourceName: namespaces/transparency-dev-playground/services/ci-static-ct] Ready condition status changed to True for Service ci-static-ct.
DEFAULT 2024-11-18T20:23:57.587443Z I1118 20:23:57.588669 1 gcp.go:580] Consuming from 0
DEFAULT 2024-11-18T20:23:57.596850Z I1118 20:23:57.598287 1 gcp.go:618] Found no rows to sequence