[analytics] introduces constants

[pq]

Follow-up from #8597. Introduces constants.

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[helin24]

I might expect these to be namespaced, e.g. ACTION_PLACE or AnalyticsConstants.Actions.PLACE

[pq]

My sense is that's unneeded since action-ness is encoded in the TYPE property already? Anyway, for sure, let's talk about it and do a full audit before we start actually capturing any data. Thanks!

[helin24]

Ah true! Yes, sgtm