IIS/ANCM: UNC `stdoutLogFile` causes invalid directory creation (ERROR_BAD_PATHNAME)

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Describe the bug

When `stdoutLogFile` is set to a UNC path (e.g. `\\SERVER\path\stdout.log`), ANCM canonicalizes the path to the extended `\?\UNC\SERVER\path\stdout.log_...` form and then attempts to create path segments starting at the wrong offset. This leads to an attempt to create the server-only path (`\?\UNC\SERVER`) which fails with `ERROR_BAD_PATHNAME` (0x800700A1) and prevents the log file from being created.

### Expected Behavior

The log file should have been created properly.

### Steps To Reproduce

1. Configure an ASP.NET Core app hosted by IIS/ANCM with `stdoutLogEnabled="true"`.
2. Set `stdoutLogFile` to a UNC path, for example:

```xml

```

3. Start the site (IIS) and observe the Windows Event Log for ANCM errors.

Event log contains an error similar to:

`Could not create stdoutLogFile \?\UNC\SERVER\path\stdout.log_..., ErrorCode = '0x800700a1'`

- The failure occurs during `EnsureDirectoryPathExists` (before `CreateFileW`) when `CreateDirectory` is called for `\?\UNC\SERVER`.

### Exceptions (if any)

_No response_

### .NET Version

v10.0.4 but it also applies to other versions and main HEAD

### Anything else?

Affected code: `src/Servers/IIS/AspNetCoreModuleV2/CommonLib/file_utility.cpp` (`FILE_UTILITY::EnsureDirectoryPathExists`) and `IISLib::MakePathCanonicalizationProof`.

Originally reported to HTTP Bridge module for IIS as https://github.com/lextudio/httpbridge/issues/9