Use web vitals attribution build for better INP tracking data

[mehigh]

Fixes - https://xwp-co.atlassian.net/browse/INITS-2416

In a recent thread, there's a reference to the "attribution build" which can provide more information on the INP tracked information:
https://twitter.com/tunetheweb/status/1764757818303717863

We're loading the standard web-vitals library ourselves
https://github.com/xwp/site-performance-tracker/blob/master/js/src/measure-web-vitals.js#L2

As a side-effect of this, we'll need to update our switch to deliver the CLS / INP and LCP attribution instead of calculating ourselves "which" attribution should be reported:
https://github.com/xwp/site-performance-tracker/blob/master/js/src/send-to-analytics.js#L103-L140