Replace use of CollapseCombinedPath with CollapseFullPath

CollapseCombinedPath was introduced by commit 551d3343 where the existing CollapseFullPath should have been used instead. Then its use proliferated slightly. Since CollapseCombinedPath is less widely used and less robust (see issue #19049 (closed)), use CollapseFullPath everywhere instead and drop CollapseCombinedPath.

Fixes: #19050 (closed)