Adjust the search priority of the vcpkg executable in the package-manager/auto-setup.cmake script.

Adjust the search priority of the vcpkg executable in the [package-manager/auto-setup.cmake|https://github.com/qt-creator/qt-creator/tree/master/src/share/3rdparty/package-manager] script.

{}Reasoning:{}
Currently, Qt Creator's auto-setup script prioritizes globally installed instances of vcpkg over local project-specific ones. This behavior can be problematic, especially when using {}MSVC on Windows{}, as Visual Studio comes bundled with a pre-installed version of `vcpkg`. The bundled version is frequently chosen by the script, even when a different version exists within the project's directories.

{}Proposed Change:{}
Modify the search order so that the script prioritizes {}local project directories{} before checking the global environment. Specifically, it should look in:
1. {}`<project_root>/vcpkg`{}
2. {}`<project_root>/3rdparty/vcpkg`{}
3. *Global vcpkg instances (`$ENV{VCPKG_ROOT}` and system paths)*

{}Benefits:{}

• Allows users to override the global `vcpkg` instance with a local one.
• Helps prevent conflicts with the {}pre-bundled{} Visual Studio `vcpkg`, which is {}not frequently updated{} and may cause compatibility issues.
• Offers more flexibility in managing different versions of `vcpkg` per project.