Use Google Analytics to track individual API's usage

[newgene]

With the new release of biothings sdk package v0.12.0, we now support the API usage tracking with the latest Google Analytics 4 (see this issue #221).

This issue is meant to adopt the new GA4 tracking feature in this repo, test the current tracking behavior and decide if any additional customization is needed for the specific tracking needs of this application.

Different from our other BioThings API applications, typically just one API per applications, this pending.api application hosts multiple BioThings APIs, each hosted under a sub-path indicating the data source name, e.g. this one: https://biothings.ncats.io/hpo. The expected behavior is to track the API usage individually under the same GA4 account, in addition to the overall tracking stats we can track already.