autofill: don't prefix autofill email pixels with m.mac. (#2808)

Task/Issue URL:
https://app.asana.com/0/1206682621538333/1207380134103391/f
Tech Design URL: N/A

Pixels fired for email autofill use-cases are intentionally not prefixed
with `m.mac.`, though the historical reason isn't clear to me. The
migration to PixelKit for pixel management[^1] caused those
email-related pixels to be prefixed. Wrap email-related JS pixels in
`NonStandardEvent`s to prevent that prefixing, to restore their original
intended names.

[^1]: d885fd0 (PixelKit adoption (#2557), 2024-04-17)

DuckDuckGo/Autofill/ContentOverlayViewController.swift

@@ -325,7 +325,7 @@ extension ContentOverlayViewController: SecureVaultManagerDelegate {
 
             self.emailManager.updateLastUseDate()
 
-            PixelKit.fire(GeneralPixel.jsPixel(pixel), withAdditionalParameters: pixelParameters)
+            PixelKit.fire(NonStandardEvent(GeneralPixel.jsPixel(pixel)), withAdditionalParameters: pixelParameters)
         } else {
             PixelKit.fire(GeneralPixel.jsPixel(pixel), withAdditionalParameters: pixel.pixelParameters)
         }