This should reduce (but not completely eliminate) gradual audio desyncs in dumps. This also allows for accurate sample rates for the GameCube.
Completely eliminating gradual audio desyncs will require resampling to an integer sample rate, as nothing seems to support a non-integer sample rate.

SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.

The class NonCopyable is, like the name says, supposed to disallow
copying. But should it allow moving?

For a long time, NonCopyable used to not allow moving. (It declared
a deleted copy constructor and assigment operator without declaring
a move constructor and assignment operator, making the compiler
implicitly delete the move constructor and assignment operator.)
That's fine if the classes that inherit from NonCopyable don't need
to be movable or if writing the move constructor and assignment
operator by hand is fine, but that's not the case for all classes,
as I discovered when I was working on the DirectoryBlob PR.

Because of that, I decided to make NonCopyable movable in c7602cc,
allowing me to use NonCopyable in DirectoryBlob.h. That was however
an unfortunate decision, because some of the classes that inherit
from NonCopyable have incorrect behavior when moved by default-
generated move constructors and assignment operators, and do not
explicitly delete the move constructors and assignment operators,
relying on NonCopyable being non-movable.

So what can we do about this? There are four solutions that I can
think of:

1. Make NonCopyable non-movable and tell DirectoryBlob to suck it.

2. Keep allowing moving NonCopyable, and expect that classes that
   don't support moving will delete the move constructor and
   assignment operator manually. Not only is this inconsistent
   (having classes disallow copying one way and disallow moving
   another way), but deleting the move constructor and assignment
   operator manually is too easy to forget compared to how tricky
   the resulting problems are.

3. Have one "MovableNonCopyable" and one "NonMovableNonCopyable".
   It works, but it feels rather silly...

4. Don't have a NonCopyable class at all. Considering that deleting
   the copy constructor and assignment operator only takes two lines
   of code, I don't see much of a reason to keep NonCopyable. I
   suppose that there was more of a point in having NonCopyable back
   in the pre-C++11 days, when it wasn't possible to use "= delete".

I decided to go with the fourth one (like the commit title says).
The implementation of the commit is fairly straight-forward, though
I would like to point out that I skipped adding "= delete" lines
for classes whose only reason for being uncopyable is that they
contain uncopyable classes like File::IOFile and std::unique_ptr,
because the compiler makes such classes uncopyable automatically.

Reduces the number of files that need to be recompiled
when making changes to FileUtil.h.