feat: Set Datadog resource name to just the handler in all apps

[timmc-edx]

This switches us from method+urlpattern resource naming (e.g. GET ^/) to using handler (e.g. lms.djangoapps.branding.views.index).

This is applied to the root span as the resource_name tag. As method and urlpattern are available on the root span as http.method and http.route but there doesn't seem to be any other way to get the handler info, this is our only option for ensuring that the handler will be available as a tag (without having to parse after the fact or write more custom code.)

Part of edx/edx-arch-experiments#620

Configuration Pull Request

Make sure that the following steps are done before merging:

• Have a Site Reliability Engineer review the PR if you don't own all of the services impacted.
• If you are adding any new default values that need to be overridden when this change goes live, update internal repos and add an entry to the top of the CHANGELOG.
• Performed the appropriate testing.
• Think about how this change will affect Open edX operators and update the wiki page for the next Open edX release if needed

[schenedx]

👍