DiscIO: Remove redundant casts

In PPCTables.cpp, the code is currently unused so I was unable to test it.

In CustomPipeline.cpp, a pointer to member function cannot be used due to 16.4.5.2.1 of the C++ Standard regarding "addressable functions". https://eel.is/c++draft/namespace.std#6

In Fs.cpp and DirectoryBlob.cpp, these examples used projections in a previous iteration of this commit, but no longer do. Still, they remain in this commit because the PR they would actually belong to is already merged.

In LabelMap.cpp, the code is currently unused so I was unable to test it.

In WiiUtils.cpp, the magic value `1u` was replaced by the constant value `DiscIO::PARTITION_UPDATE`.

In DITSpecification.cpp, MaterialAsset.cpp, and ShaderAsset.cpp, lambda predicates were replaced by pointers to member functions because ranges algorithms are able invoke those.

In NetPlayClient.cpp, the non-trivial `NetPlay::Player` elements were being passed by value in `NetPlayClient::DoAllPlayersHaveGame()`. This has been fixed.

In WIABlob.cpp, the second example's predicate was returning the `std::optional` by value instead of implicitly converting it to a bool. This has been fixed.

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