Orphan page in breadcrumbs should use navtitle instead of doctitle

If a page is found in the navigation, the breadcrumb entries show the navtitle of each page (which defaults to the doctitle, aka page title, if the navtitle is not specified). However, if a page is not found in the navigation (an orphan), then the doctitle is used. To be consistent, the navtitle should always be used in this context. That gives the author control over what text is displayed in the breadcrumbs if the desire is to make it different from the doctitle.

Interesting to note that the unlisted pages extension in the docs honors the navtitle, which establishes further precedent for why the proposed behavior is correct.