chore(glean): add page's UTM parameters to pings

[LeoMcA]

Summary

https://mozilla-hub.atlassian.net/browse/MP-545
https://bugzilla.mozilla.org/show_bug.cgi?id=1851150

Problem

We can't easily attribute traffic which adds utm parameters through Glean.

Solution

Add utm parameters to our Glean pings.

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How did you test this change?

• yarn && yarn dev
• visit a page locally, appending utm parameters, e.g. the ones given in the example on wikipedia
• observe ping: https://debug-ping-preview.firebaseapp.com/pings/mdn-dev/4ada8297-949e-4904-9bc8-39d0d8922b0f

@fiji-flo after sending this ping, I realised we already sorta send utm parameters to glean, through the page.path metric - since we'll now be sending these in a structured form, should I wipe utm_ parameters out of the url we send in that metric (or even not send any query parameters in page.path at all, to keep it "clean"?)

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.

[caugner]

One nit, otherwise LGTM.

[LeoMcA]

@fiji-flo after sending this ping, I realised we already sorta send utm parameters to glean, through the page.path metric - since we'll now be sending these in a structured form, should I wipe utm_ parameters out of the url we send in that metric (or even not send any query parameters in page.path at all, to keep it "clean"?)

@fiji-flo I have a vague memory of discussing this and you saying to clean the page.path metric, but I don't remember for sure (and couldn't find a record of it). I'll merge this for now, and can open another PR doing that if we want to do that.