Show install path restrictions directly in the installer

[lazka]

We have these restrictions on the main page for the install location "Enter your desired Installation Folder (short ASCII-only path on a NTFS volume, no accents, no spaces, no symlinks, no subst or network drives, no FAT).".

We should show this on the installer page where one selects the location.

[lazka]

Because I stumbled over it: The qt installer framework has some related options for this: AllowNonAsciiCharacters, AllowSpaceInPath https://doc.qt.io/qtinstallerframework/ifw-globalconfig.html

They validate the target path, show an error message and don't allow the user to continue if it fails.

Since our limitations depend on the software being used, and ideally we want to improve things I'm still in favor of just having a note there and not disallowing it completely.