iOS support

[adhorodyski]

Goal of this is to provide the basic core functionalities on iOS, same way we did for Android.

• Configure the global SDK's singleton (native) from the static init() method for Traces and Metrics
• Allow exporting JS provided Traces and Metrics with the native SDK through the Turbo Module:
  • exportTraces
  • exportMetrics

[adhorodyski]

An example from the Swift SDK: https://github.com/open-telemetry/opentelemetry-swift/blob/main/Examples/OTLP%20Exporter/main.swift that might be helpful.