Optimize NIO path resolution in `PathEditor`

[jhoeller]

PathEditor has historically accumulated a rather nuanced code path where it tries to handle Spring resource resolution, file URLs, NIO path URIs as well as NIO path Strings. The latter is a fallback under certain conditions which led to a regression and an immediate revision in 5.3.x (#26575/#26702). Following up on that, we can restore an optimization that the original fix (#26575) had, namely to shortcut non-file resolution toward an NIO path String.

[github-actions]

Fixed via 3781ba2