Code Review Bench PR #31027 - Refactor FXIOS-12796 [Swift 6 Migration] Fix main actor isolation warnings that are Swift 6 errors in the XCUITests suite - Batch 2

[tomerqodo]

Code Review Bench PR mozilla-mobile#31027

Original PR Title: Refactor FXIOS-12796 [Swift 6 Migration] Fix main actor isolation warnings that are Swift 6 errors in the XCUITests suite - Batch 2
Original PR Description: ## 📜 Tickets
Jira ticket
Github issue

💡 Description

• Fix setUp/tearDown warnings in the XCUITests suite by using the async throws version of the methods
• Fix main actor isolation warnings for some local state with @MainActor

See the Swift 6 Migration channel (#tmp-swift-6-migration) for details on how to migrate the setUp and tearDown methods.

Batch 1: mozilla-mobile#31025

cc @Cramsden @lmarceau @dataports

📝 Checklist

• I filled in the ticket numbers and a description of my work
• I updated the PR name to follow our PR naming guidelines
• I ensured unit tests pass and wrote tests for new code
• If working on UI, I checked and implemented accessibility (Dynamic Text and VoiceOver)
• If adding telemetry, I read the data stewardship requirements and will request a data review
• If adding or modifying strings, I read the guidelines and will request a string review from l10n
• If needed, I updated documentation and added comments to complex code
  Original PR URL: Refactor FXIOS-12796 [Swift 6 Migration] Fix main actor isolation warnings that are Swift 6 errors in the XCUITests suite - Batch 2 mozilla-mobile/firefox-ios#31027