Data: Add metrics reporter to generic scan builder

[alexandrefimov]

This adds a delegating metricsReporter method to IcebergGenerics.ScanBuilder so callers can configure scan metrics reporting without accessing the underlying TableScan directly.

This follows the API shape proposed in #14654, which was closed as stale, and adds focused test coverage for the generic read path.

Closes #14875.

Tests (JDK 21):

• ./gradlew :iceberg-data:test --tests org.apache.iceberg.data.TestLocalScan.testScanMetricsReporter
• ./gradlew :iceberg-data:test --tests org.apache.iceberg.data.TestLocalScan
• ./gradlew :iceberg-data:spotlessCheck
• ./gradlew :iceberg-data:revapi
• ./gradlew :iceberg-data:javadoc

[alexandrefimov]

The only failing check is core-tests (17), caused by the known flaky TestHadoopCommits > testConcurrentFastAppends(File) timeout. Could someone with permissions please rerun the failed job?