Add UTM card to Stats

[kean]

Description

Closes CMM-597: Add UTM sources chart.

Similarly to #25176, it "simply" introduces one more "Top List" item type: "UTM". I used the Calypso codebase as a reference for implementing it. There is nothing out of the ordinary in this PR.

Testing instructions

I tested it end-to-end on one of the production sites. Ping me if you need more details.

Screenshots

[dangermattic]

	1 Warning
⚠️	This PR is larger than 500 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

Generated by 🚫 Danger

[kean]

I'm not sure why the web has a different blue. I thought I used the same one in the app. It's now clear side-by-side it's not. I'll look into ways to make them more consistent.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	30680
	Version	PR #25178
	Bundle ID	org.wordpress.alpha
	Commit	f48ea71
	Installation URL	13fq71hqqhq0o

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	30680
	Version	PR #25178
	Bundle ID	com.jetpack.alpha
	Commit	f48ea71
	Installation URL	6v1mfcfoaohbg

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[crazytonyli]

Something like this, so that we don't need to manually parse the quotes and square brackets?

let decoder = JSONDecoder()
let data = key.data(using: .utf8)
if let values = try? decoder.decode([String].self, from: data) {
  return values
}
if let string = try? decoder.decode(String.self, from: data) {
  return [string]
}

[kean]

It's defensive code. It does look cleaner with decoder. Updated.

[sonarqubecloud]

Quality Gate passed

Issues
11 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
7.8% Duplication on New Code

See analysis details on SonarQube Cloud