Fix reading Wii FST size (for real this time)

GC games with long names store two variations of the name in
opening.bnr. This makes the shorter of those names available.
For volumes other than GC discs, prefer_long is ignored.

ISOFile and GameFile were using IsWiiDisc() and IsWadFile() to set
an enum value. The volume might as well return an enum directly.

I increased the Qt CACHE_REVISION because m_platform now is saved as u32
instead of int, but increasing the wx CACHE_REVISION is not necessary.

Disc number is changed from bool to u8, and revision is changed from
int to u16 (WADs can use all 16 bits, but discs can only use 8 bits).

Fix reading Wii FST size

This is intended to better separate it from GetNames and to clarify
that this name originally wasn't meant to be shown to users.
The ISOProperties GUI is also updated, mainly because labeling
the long banner name "short name" was confusing.

This makes Dolphin display the same names as the Disc Channel.

Having some data available in banner loaders and some other data
data available in volumes gets messy, especially with GetNames(),
which is available in both but returns different results
depending on which one is used. This change drops support
for reading names and descriptions from Wii save data.