Add tool to test DSP instructions

[JayFoxRox]

This should make it easier to test DSP instruction behaviour.

Can be ran like this with debug bios:

A56=/home/user/a56/a56 XBOX=localhost:8731 ./dsp_instruction_test.py dsp_instruction_tests/*-test.json 

(Requires a56; example was with -redir tcp:8731::731 in XQEMU CLI)

For test syntax, check the examples. Further changes to input / output syntax are likely.

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Most critical missing features / known issues:

• Memory can not be set as input / output, no fatal error is generated
• Some registers are blacklisted / ignored, no fatal error is generated
• DSP assembler errors are silently ignored, no fatal error is generated
• JSON and assembly parser issues are not reported properly
• Output folder is same as input folder, so it's hard to generate 2 outputs for different machines
• No tool to compare JSON output files
• Code is ugly