Makes the enum values strongly-typed and prevents the identifiers from
polluting the PowerPC namespace. This also cleans up the parameters of
some functions where we were accepting an ambiguous int type and
expecting the correct values to be passed in.

Now those parameters accept a PowerPC::CPUCore type only, making it
immediately obvious which values should be passed in. It also turns out
we were storing these core types into other structures as plain ints,
which have also been corrected.

As this type is used directly with the configuration code, we need to
provide our own overloaded insertion (<<) and extraction (>>) operators
in order to make it compatible with it. These are fairly trivial to
implement, so there's no issue here.

A minor adjustment to TryParse() was required, as our generic function
was doing the following:

N tmp = 0;

which is problematic, as custom types may not be able to have that
assignment performed (e.g. strongly-typed enums), so we change this to:

N tmp;

which is sufficient, as the value is attempted to be initialized
immediately under that statement.

Amends the function names to follow our coding style.

Also clean up the way the system menu label is updated. We don't want
to access the NAND while emulation is running, and especially not
that many times per second on an unpredictable timing.

Old versions of Dolphin are so broken regarding NAND handling that
we need this to repair common issues and avoid issues with titles
like the System Menu or the Wii Shop.

This isn't an exhaustive check, but this will catch most issues
and offer to fix them automatically (if possible).

This was inconsistent with the other three regions
and with DolphinQt2.