chore(functional-tests): upgrade eslint-plugin-playwright to 2.x
Because: * The 2.x eslint-plugin-playwright rules flag faults in the tests * denormalizeStoredEmail used a Node variable in page.evaluate This commit: * Upgrades eslint-plugin-playwright to ^2.12.1 in functional-tests * Fixes denormalizeStoredEmail so it uppercases the stored email * Uses web-first assertions where the new rules ask for them Closes FXA-11367