windows: fix CreateFile() calls to support long filenames

It makes them work in Schannel's CA bundle loader, and curl tool's
set/get file timestamp operations (e.g. in `-R`/`--remote-time`). Also
to match file open operations, that already support long filenames.

E.g. when using `--remote-time`, fixing:
```
Warning: Failed to set filetime 1741363917 on outfile: CreateFile failed:
Warning: GetLastError 0x00000003
```

The special long filename logic is necessary to support Windows releases
prior to Windows 10 v1607. With the latter, it's possible to opt-in to
this behavior via a manifest setting. Note that Windows itself also needs
to opt-in to support this. Finally note that curl itself needs passing
`--globoff` to let long filenames through, pending #20044 and #20046.

Refs:
https://learn.microsoft.com/windows/win32/api/fileapi/nf-fileapi-createfilea
https://learn.microsoft.com/windows/win32/fileio/maximum-file-path-limitation

Ref: #8361
Inspired by: #19286
Inspired-by: Mathesh V
Closes #19286
Closes #20040

lib/curlx/fopen.h

@@ -35,6 +35,15 @@
 int curlx_fseek(void *stream, curl_off_t offset, int whence);
 
 #ifdef _WIN32
+#ifndef CURL_WINDOWS_UWP
+HANDLE curlx_CreateFile(const char *filename,
+                        DWORD dwDesiredAccess,
+                        DWORD dwShareMode,
+                        LPSECURITY_ATTRIBUTES lpSecurityAttributes,
+                        DWORD dwCreationDisposition,
+                        DWORD dwFlagsAndAttributes,
+                        HANDLE hTemplateFile);
+#endif /* !CURL_WINDOWS_UWP */
 FILE *curlx_win32_fopen(const char *filename, const char *mode);
 FILE *curlx_win32_freopen(const char *filename, const char *mode, FILE *fh);
 int curlx_win32_stat(const char *path, struct_stat *buffer);