Don't synthesize page load on navigations that used to get ignored

We no longer ignore navigations (NAVIGATION_TYPE_NAV_IGNORE, where we
commit the navigation but don't actually create a NavigationEntry for
the navigation) after crrev.com/c/3237491 and crrev.com/c/3237493. This
can cause NavigationStateChanged calls to be fired in more occasions
than before, which can result in more onPageStarted, onPageFinished etc
calls on Android WebView (through
postSynthesizedPageLoadingForUrlBarUpdate) which is unexpected for some
apps (see linked bug).

This CL marks the navigations that used to get ignored and
NavigationEntries that used to not exist before the introduction of
initial NavigationEntries, so that WebView can preserve its old
behavior by continuing to "ignore" the marked NavigationStateChanged
calls.

Bug: 1277414
Change-Id: I82692bae155775ff95ecf720b7ccd86b61d51467
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3347483
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/main@{#953393}