Because:
* We are making a few UX changes to the beginning of the desktop pairing flow
This commit:
* Adjusts the "pair" page when coming from CAD to display a new "Sync your Firefox experience" radio button question
* On selection and submission of this form, conditionally opens FF pair if they already have a mobile device, or displays the mobile QR code if they need to download and then on "continue" opens FF pair
* Adds a back button
* Adds new SVGs, ran through SVGO
* Adds 5x new front-end Glean metrics events
closes FXA-9609
closes FXA-9590
closes FXA-9591
Lauren Zugai