Metrics labels and headers discard values containing colons

Broker, Proxy, and Controller metrics configuration split label and OTLP header entries on every colon. Values such as https://collector:4317 are considered invalid and silently discarded. Expected behavior: split each entry on the first colon so the complete value is preserved.

Locate the metrics configuration parsing used by the Broker, Proxy, and Controller for label and OTLP header entries. Start by tracing where entries are split, then verify that values such as https://collector:4317 preserve everything after the first colon and are no longer discarded.

Written by the indexing model from the issue text.