Bigtable: Client side metrics opt-out is not honored in BigtableChannelPrimer

[premm01]

Issue
Since 2.38.0, client-side metrics have been enabled by default.
The docs here state that one needs to pass a NoopMetricsProvider.INSTANCE in BigtableDataSettings to opt out of the metrics.
However client side metrics are anyways enabled during channel priming as BigtableChannelPrimer creates its own EnhancedBigtableStubSettings.

Impact
Local testing with Bigtable test container has been impacted by the timeout of 1 minute used in BigtableCloudMonitoringExporter as the exporter is either unable to reach or authenticate with the cloud monitoring endpoint.
Production instances are emitting metrics even if an opt-out was added.

Known workaround
For tests, using the deprecated configuration to disable channel refreshes prevents creation of BigtableChannelPrimer, bypassing the issue.
This option, however, is due to be removed in future.

Bigtable library version
2.44.0 but all versions since 2.38.0 should be affected