* Adds ab test controller with a fullScreenVsPopup test
* Add migration for fullScreenVsPopup state
* Move abtest state under an 'abtests' object.
* MetaMask shows fullScreen group of a/b test unapproved txs in a full browser tab
* Ensure cancel metrics event in confirm-transaction-base.component.js is sent in all cases
* Switch to existing tab for unapproved tx if it exists when opening in full screen
* Send metrics event for entering a/b test from confirm screen
* Fix lint, unit and integration tests related to a/b test code
* Remove unnecessary tabs.query call in triggerUiInNewTab
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