feat: improve store_trace_reason with extract parameter store_trace_reason() used embedded code to extract reason based on the location passed to the function. This change adds support for extract keyword that is a Python expression eval'ed when the underlying function/method is called. All callers now set the extract parameter. The prior embedded code has been removed from store_trace_reason(). Failure to eval the expression results in an roundup.logcontext error severity log. Also updated docs. Also replaced env['REQUEST_URI'] with env['PATH_INFO'] for web based entry points as REQUEST_URI isn't documented as a required key and some other front end (e.g. zope, cgi) might not supply this.