KIP-344 — The auto-generated client id should be passed to MetricsReporter

Discarded Kafka 2.1 ClientMetrics

Fixes a bug where the auto-generated `client.id` is not passed to `MetricsReporter.configure()` when the user has not explicitly set `client.id`. The `MetricsReporter` receives the config map at initialization, but the auto-generated ID is created after config parsing, so it is missing from the map passed to the reporter. (Resolved as a bug fix, no KIP required.)

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