+ a surprise `std::memcpy` in VolumeVerifier.cpp.

A vector of length 0 can have a null data pointer, which causes UB when
passed to memcpy, so only copy when we actually have data to copy. This
caused crashes in certain cases when compiling Dolphin with Clang and
LTO enabled.

A deep-copy method CopyReader has been added to BlobReader (virtual) and all of its subclasses (override). This should create a second BlobReader to open the same set of data but with an independent read pointer so that it doesn't interfere with any reads done on the original Reader.

As part of this, IOFile has added code to create a deep copy IOFile pointer onto the same file, with code based on the platform in question to find the file ID from the file pointer and open a new one. There has also been a small piece added to FileInfo to enable a deep copy, but its only subclass at this time already had a copy constructor so this was relatively minor.

Just some clarifications and typo fixes.

Previously, we had WBFS and CISO which both returned an upper bound
of the size, and other formats which returned an accurate size. But
now we also have NFS, which returns a lower bound of the size. To
allow VolumeVerifier to make better informed decisions for NFS, let's
use an enum instead of a bool for the type of data size a blob has.

Needed for the next commit. NFS disc images are hashed but not encrypted.

While we're at it, also get rid of SupportsIntegrityCheck.
It does the same thing as old IsEncryptedAndHashed and new HasWiiHashes.