add insight server layer

[subotic]

Packages the complete insight server based on ZIO-HTTP into its own layer, that can be added to any ZIO application:

object SampleApp extends ZIOAppDefault with InstrumentedSample {

  private val insightServerConfig = InsightServerConfig(8080, 5.seconds)

  override def run: ZIO[Any with ZIOAppArgs with Scope, Any, Any] =
    program
      .provide(
        insightServerLayer(insightServerConfig),
      )
}

[atooni]

LGTM - WGYT: With the InsightLayer pushed to the API I think it would make more sense to remove the split between the InstrumentedSample and SampleApp. We want to show that Insight can be used by simply injecting a single layer ??

[subotic]

@atooni I've added the changes as discussed.