Add new AWS Lambda plugin

[imjoehaines]

Goal

This PR adds a plugin to allow Bugsnag to work in an AWS Lambda function. There is more work to do before release, such as session support, but the plugin is functional in this state

This plugin works by using the new @bugsnag/in-flight package so that it can wait for all requests to finish before allowing the Lambda to terminate. There is a default 2 second timeout, but this can be configured by the user to whatever makes sense for their app

Basic usage

const Bugsnag = require('@bugsnag/js')
const BugsnagPluginAwsLambda = require('@bugsnag/plugin-aws-lambda')

Bugsnag.start({
  apiKey: 'api key here',
  plugins: [BugsnagPluginAwsLambda]
})

const bugsnagHandler = Bugsnag.getPlugin('awsLambda').createHandler()

const handler = async (event, context) => // code goes here

module.exports.lambdaHandler = bugsnagHandler(handler)

createHandler takes an options object, with the only current option being flushTimeoutMs. This is the length of time (in milliseconds) that we will wait for requests to finish. For example:

createHandler({ flushTimeoutMs: 5000 }) // 5 seconds

Testing

Tested with unit tests and the MR tests have been updated to assert events are reported when using the new plugin

[github-actions]

@bugsnag/browser bundle size diff

	Minified	Minfied + Gzipped
Before	40.76 kB	12.57 kB
After	40.76 kB	12.57 kB
±	No change	No change

code coverage diff

Ok	File	Lines	Branches	Functions	Statements
✅	/home/runner/work/bugsnag-js/bugsnag-js/packages/in-flight/src/in-flight.js	100% (+0%)	66.67% (+16.67%)	100% (+7.69%)	100% (+0%)
✅	/home/runner/work/bugsnag-js/bugsnag-js/packages/plugin-aws-lambda/src/index.js	100% (+100%)	100% (+100%)	100% (+100%)	100% (+100%)

Total:

Lines	Branches	Functions	Statements
81.45%(+0.19%)	70.18%(+0.37%)	84.03%(+0.33%)	80.35%(+0.19%)

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