Graceful fallback for non-default NIO.2 FileSystems

[jhoeller]

As a backport ticket from #35435, we can revise FileSystemUtils.copyRecursively toward tolerating different source/destination file systems, as well as leniently handling UnsupportedOperationException from File.toPath() in DataBufferUtils as well as ResourceHttpMessageWriter.

[github-actions]

Fixed via ba52164