DeZ80 v4.0.0

This major release of DeZ80 changes the top-level visibility of some data structures with the aim of promoting verbosity where it is helpful while keeping the most basic interfaces (Instruction, InstructionDecoder, and DecodingState) available at the top level, removes some redundant interfaces (most notably InstructionDecoder::new()), and introduces DecoderState variants for displacement operands. This primarily benefits emulator/simulator applications that need to handle displacement computation cycles and could not disambiguate between displacement and non-displacement operands in indexed instructions in prior versions. For indexed bitwise instructions, IndexedBitwiseDisplacement replaces IndexedBitwiseOperand in DecoderState.

This would probably be suitable for a v1.0.0 release if I hadn't jumped the gun.

Changes:

• Update dependencies and their usage
• Clean up some minor warnings and comments
• Add some interfaces and re-exports
• Remove some interfaces and re-exports
• Distinguish displacement operands from non-displacement operands in DecodingState
• Fix a security warning for dez80_cli stemming from an abandoned dependency package