Removing Navigation objects from WebNavigationState when the navigation completes, to avoid leaking them.
<rdar://problem/109430054>
Pull request: https://github.com/WebKit/WebKit/pull/13964
Pull request: https://github.com/WebKit/WebKit/pull/14023
Committed 264449@main (9ae6f745cc3d): <https://commits.webkit.org/264449@main> Reviewed commits have been landed. Closing PR #14023 and removing active labels.