Heartbeat add NTLM to basic URL up/down testing

This request is also described here: [Beats Issue 5237 - Heartbeat support for NTLM auth](https://github.com/elastic/beats/issues/5237)

We have many internal Corp URLs that are single sign-on with Windows Authentication / NTLM. This is a pretty widespread use case for shops doing observability for internal applications. A good example is SharePoint but we have many apps that use NTLM auth.

thanks

Start with the linked Beats issue 5237 and Heartbeat's basic URL up/down testing entry point. Review how authentication is currently handled and define success as reliably checking internal URLs that use Windows Authentication/NTLM, including SharePoint-style applications.

Written by the indexing model from the issue text.