The inequality operator is automatically generated by the compiler if `operator==` is defined.

The offset-based overload hasn't been in use since
f754a1a548f2e599e4cc2d1d799f2d21b520076f.

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.

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.