feature: add before/after InvocationRequest hooks

[markwolff]

Copied from #338

Adds two InvocationRequest hooks to WorkerChannel to enable context correlation and node.js worker APM instrumentation. Sample use case for Azure Monitor node.js SDK.

• invocationRequestBefore: (context, userFunction) => contextWrappedUserFunction
• invocationRequestAfter: () => void

note: workerChannel would need to be passed to app insights in some way, i.e. in nodejsWorker.ts:

if (shouldSetupAppInsightsFunctionsIntegration) {
  require("/path/to/applicationinsights/agent/functions")
    .setupFunctionsInvocationHooks(workerChannel);
}

In App Insights SDK, setupFunctionsInvocationHooks would be defined:

workerChannel.invocationRequestBefore = (context, userFunction) => {
    // Map Functions context to AppInsights context
    const correlationContext = appInsights.startOperation(context, "Functions.JavaScript.Trigger");

    // Wrap the Function runtime with correlationContext
    return appInsights.wrapWithCorrelationContext(userFunction, correlationContext);
}

workerChannel.invocationRequestAfter = () => {
    // Do any extra cleanup or flushing here
    appInsights.defaultClient.flush(); // can be async or sync
}

[mhoeger]

/azp run

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[mhoeger]

/azp run

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[mhoeger]

✅ LGTM - on registering async functions, since it's not like a one line change, let's just cross that bridge when we get there.

Thanks!!