Add new ApplicationInsights lib code

[hasandogu]

unhandled was changed to Unhandled as well.

[msftclas]

Thank you for your submission, we really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

❌ hasandogu sign now
_{You have signed the CLA already but the status is still pending? Let us recheck it.}