Merge external repos into main repo

[jsumners-nr]

Description

There are a set of repos that provide instrumentation features within the newrelic agent. They are:

• https://github.com/newrelic/node-newrelic-aws-sdk.git
• https://github.com/newrelic/node-newrelic-koa.git
• https://github.com/newrelic/newrelic-node-nextjs.git
• https://github.com/newrelic/node-newrelic-superagent.git

At some point in the past, it was decided these should be in their own repository. Presumably, the thinking was that clients who need fixes in the specific instrumentations they provide could update those modules without having to wait for a new release of newrelic. That may be true, but the reality is that it isn't worth the complications it brings. Namely:

1. There are circular dependencies between the external packages and newrelic. As an example the difficulty this causes see fix: Fixed instrumenting the same module installed in different locations #2104. It was difficult to orchestrate because changes needed to be made in at least the aws-sdk package the required coordinating with a new release of newrelic merely to move development of the PR along.
2. We cannot make internal changes to newrelic without impacting the releases of the external modules. As an example, chore: Attached specs to the Shim.prototype for use in custom instrumentation and instrumentation outside of the agent #2038 resulted in a new version of both newrelic and aws-sdk. Folks updated aws-sdk without updating newrelic and found themselves in a broken state because aws-sdk couldn't find the code it needed.

To fix these issues, and make our development of newrelic easier and more robust, we need to migrate these modules into the main newrelic code base.

Ideally, we will keep the histories of those external repos by utilizing --allow-unrelated-histories.

Note: https://github.com/newrelic/node-newrelic/blob/c32cb2739ece3adcf5bd42e646071b3f59e691ba/test/versioned-external/external-repos.js should be updated as repos are migrated.

[workato-integration]

https://new-relic.atlassian.net/browse/NR-256139

[workato-integration]

Work has been completed on this issue.