Add LoongArch64 support

[CSharperMantle]

Add auto-generated LoongArch64 decoding tables.

The scripts and data sources used to generate the tables can be found at https://gist.github.com/CSharperMantle/7a6615aa2cfcfcf7ce344816db2dc5b3 and https://github.com/loongson/LoongArch-Documentation/blob/e0d6592229d9e00e512bd28b688a7f20b171714f/docs/LoongArch-Vol1-EN/table-of-instruction-encoding.adoc.

Preferred merging strategy: Squash.

Remark. It is not expected to work before #31 is resolved due to some mnemonics containing underscores.

Checklist

• Initial implementation.
• Add basic demonstrative test cases.
• Add tests for each instruction format.
• Resolution of Allow literal dots in instruction mnemonics? #31.

[FRoith]

looks good, the only possible improvement I can suggest right now is more randomized test cases, since I can't easily verify the large toml file

but those can be added later too, it looks good enough to merge imo

[CSharperMantle]

more randomized test cases

Talking about tests, is it okay to share some bits about how RV test cases are generated?

AFAIK LoongArch does not have a standardized testbench like https://github.com/riscv-software-src/riscv-tests, so maybe yet another script is needed.

[FRoith]

Talking about tests, is it okay to share some bits about how RV test cases are generated?

I generated tests by identifying the variable parts of every Instruction, and generating a couple of random bit patterns I could then decode with objdump (or whatever decompiler you want the instructions to match), parse the result and create the tests that way.

[FRoith]

but if it's alright, I will merge this in a few minutes

[CSharperMantle]

I think I will add generated tests in a later, separate PR. So glad that this one can 🚀!