Improve test coverage for assembly

[fabianschuiki]

Add reader/writer test cases for every single instruction in all its variations. Probably the easiest way to perform the check would be to call llhd-conv with LLHD as input and output format, then check that the output matches the input.

Todo

• add
• alias
• and
• array
• br
• call
• con
• const
• del
• drv
• eq
• extf
• exts
• halt
• insf
• inss
• inst
• ld
• mux
• neg
• neq
• not
• or
• phi
• prb
• reg
• ret
• sdiv
• sge
• sgt
• shl
• shr
• sig
• sle
• slt
• smod
• smul
• srem
• st
• struct
• sub
• udiv
• uge
• ugt
• ule
• ult
• umod
• umul
• urem
• var
• wait
• xor