Case sensitive file exist check

[keywan-ghadami-oxid]

When working on a operating system with case insensitive filesystem
the programmer needs a warning if hir has give the file a different case then in the metadata file.

The additional check from the kiwi edition will only work for the legacy autoloader when not using namespace.
https://github.com/TeamPull/oxid-module-internals/commit/b9f496fa48cd843c695770174889e3a5f1797300
For namespace a additional check could be implemented, that depends on the autoloader setting in the composer file of the module.