Support configurable error reporting based on status code in net/http

[nakkamarra]

Many of the other frameworks supported in contrib offer something along the lines as what the echo dd-trace-go package offers here, where a user can provide a function to determine whether or not a given trace should be considered an error (i.e a user wants to report 400s as errors or want to not report a single specific code for some reason)

I suggest we support something similar here and update this check to use the new configured function instead. This way, explicit usage of TraceAndServe(...) can supply a function for it's ServeConfig (my use case), and the contrib/net/http package's dependence upon this function can also provide a functional option to it's ServeMux's configuration that can simply pass right through to this TraceAndServe function.

LMK what you think! Thanks

[mtoffl01]

Responded on the PR #2882. Let's keep the discussion over there, and I will close this proposal.