Add support for INP

[ceckoslab]

The EventTiming Boomerang JS plugin supports INP: https://github.com/akamai/boomerang/blob/master/plugins/eventtiming.js

It will be a great idea to add INP to Basic RUM as more and more people are interested in monitoring and opitmizing INP.

These are the current Boomerang JS parameters that contain INP data:

• et.inp: Interaction to Next Paint (full page, on Unload beacon)
• et.inp.e: INP target element
• et.inp.t: INP timestamp that the interaction occurred
• et.inp.inc: Incremental Interaction to Next Paint (for the Page Load and each SPA Soft nav)
• et.inp.inc.e: Incremental INP target element
• et.inp.inc.t: Incremental INP timestamp that the interaction occurred