Bug 1980474 - Add SearchEngineUrl::exclude_partner_code_from_telemetry to search config

[0c0w3]

This is a speculative PR that adds SearchEngineUrl::exclude_partner_code_from_telemetry so that BrowserSearchTelemetry can know it should exclude the partner code for Google Lens from sap.counts. It's based on #6854.

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[Standard8]

I think this is a reasonable way of handling this. I can't think of anything better. We might need to have a specific partner_code field within the URL at some stage, but for now, I think this works and is flexible for future.

One thing I did notice, is that I think an entry needs adding in SearchEngineUrl::merge, as the value isn't being propagated up.

I think we'll probably need some tests as well.

[Standard8]

Thank you for the updates.

[0c0w3]

Thanks, I'll squash these commits and merge.