Bug 1868469 - Update the url immediately for existing engineSession

When we have an existing `engineSession` we use an optimized route to
load the url without needing to dispatch the load action. This is still
a valid performance improvement to make page loads faster.

However, in this code path we do not end up update the url in the state
until we get back a response from the Engine. This gives a perceived
performance loss of slow browsing. Updating the url gives UI components
an immediate update which reflects a change that would have been entered
by the user.

It was considered if we should do this in a middleware, but since this
is an optimized route, we should not wait for the middleware to process
the action before we perform the state update.

app/src/androidTest/java/org/mozilla/fenix/ui/CrashReportingTest.kt

@@ -85,7 +85,7 @@ class CrashReportingTest : TestSetup() {
             verifyPageContent(tabCrashMessage)
         }.openTabDrawer {
             verifyExistingOpenTabs(firstWebPage.title)
-            verifyExistingOpenTabs(secondWebPage.title)
+            verifyExistingOpenTabs("about:crashcontent")
         }.closeTabDrawer {
         }.goToHomescreen {
             verifyExistingTopSitesList()