Fix detach IPCs races against navigation commit with navigation queueing

With navigation queueing, a pending commit navigation is never
cancelled. If a pending commit navigation races with the frame being
removed from the DOM, the renderer process committing the navigation can
end up missing the detach: in the browser process, the detach is
replicated to the other renderers by deleting the RenderFrameProxyHosts
for the FrameTreeNode. However, the committing renderer process will no
longer have a RenderFrameProxy after the commit completes in its
process, so it will never hear about the detach.

The fix is to also call `DeleteRenderFrame()` when discard pending
commit speculative RFHs, rather than assuming that the pending commit
RenderFrame will be implicitly cleaned up.

Bug: 332746903
Change-Id: I0e8c48b0c17271cdf974ec40ff6a479346581def
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5460976


Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1289587}