Force WIMBOOT mode for an ISO

[longpanda]

Try this CI release: https://github.com/ventoy/Ventoy/actions...2458653039
https://www.ventoy.net/en/doc_grub2boot.html

It will auto use wimboot mode if the ISO file name contains _VTWIMBOOT suffix. (e.g. win11_english_x64_VTWIMBOOT.iso)