Introduce `enableMetricKit` option in React Native SDK

[philprime]

Expose an enableMetricKit option in the React Native SDK and propagate it to the underlying Apple/Cocoa SDK.

Context from the discussion:

• enableMetricKit can already be enabled through native initialization, but it is not exposed in the React Native SDK options.
• MetricKit app hangs are distinct from App Hangs V2.
• The goal is to officially support this option in React Native so it can be used directly from SDK configuration.

[linear-code]

RN-711