GetFileList() no longer report world files

[Even Rouault]

Since r28907, world files are no longer listed by the generic GetFileList() implementation due to an inverted logic test... (the original intent was avoid stat'ing those sidecar files in /vsicurl/foo?bar case)

Not sure if it is a bad thing as previously world files were sometimes listed even when they are not used. For example an ECW file that has internal georeferencing will ignore its world file.

[Even Rouault]

In 34438:

GDALDataset::GetFileList(): remove dead code.

Up to r28907, this function used to report side car world files. But r28907 broke
this behaviour due to a logic error (it should have tested
GDALCanFileAcceptSidecarFile(), and not its reverse). But fundamentally, the
'broken' behaviour is not bad, since there's no guarantee that a .wld will be
used. It should be the responsibility of the driver to report it if it uses it,
which popular drivers already do.

Fixes #6169