Spring Normalize URIs returned from FileSystemResource.getURI()

Due to changes made in conjunction with #29163, the URI for a FileSystemResource returned from PathMatchingResourcePatternResolver.getResources(String) now includes an additional two slashes (file:///...) instead of one (file:/...) as was previously the case.

In order not to break existing code that expects a single leading slash, we should see if we can modify the behavior of FileSystemResource so that file: URIs returned from getURI() contain a single slash.