Improve tab lazy loading test reliability (#3645)

Task/Issue URL: https://app.asana.com/0/1199230911884351/1208926119997580/f
Tech Design URL:
CC:

Description:

This is an experimental change to improve some CI reliability, after successfully reproducing failures locally and then applying this fix to resolve them. So far, I haven't seen another failure locally after a half dozen runs, whereas before I could reproduce this almost every time.

UnitTests/Sync/SyncPreferencesTests.swift

@@ -144,9 +144,10 @@ final class SyncPreferencesTests: XCTestCase {
 
     @MainActor func testOnTurnOffSyncThenSyncServiceIsDisconnected() async {
         let expectation = XCTestExpectation(description: "Disconnect completed")
-        Task {
+        Task { @MainActor in
             syncPreferences.turnOffSync()
             XCTAssertNil(managementDialogModel.currentDialog)
+            await Task.yield()
             expectation.fulfill()
         }
         await fulfillment(of: [expectation], timeout: 5.0)

UnitTests/TabBar/ViewModel/TabLazyLoaderTests.swift

@@ -243,7 +243,7 @@ class TabLazyLoaderTests: XCTestCase {
         lazyLoader?.scheduleLazyLoading()
 
         // Then
-        waitForExpectations(timeout: 0.3)
+        waitForExpectations(timeout: 3.0)
         XCTAssertEqual(didFinishEvents.count, 1)
         XCTAssertEqual(try XCTUnwrap(didFinishEvents.first), true)
     }