As per #83040 (comment), some of the ILLink.Substitution entries may be unnecessary since corelib already compiles in a different copy of the ISAs (*.PlatformNotSupported.cs) which return constant false.

We should double check that removing these are ok and make the files shorter if possible.

-- Noting the Vector64/128/256/512 entries are needed since they do not return constant false and are instead recursive by default.