Use capstone to validate precise-output tests (#5780)

Use the capstone library to disassemble precise-output tests, in addition to pretty-printing their vcode.

cranelift/filetests/filetests/isa/aarch64/simd-pairwise-add.clif

@@ -9,9 +9,15 @@ block0(v0: i8x16):
   return v3
 }
 
+; VCode:
 ; block0:
 ;   saddlp v0.8h, v0.16b
 ;   ret
+; 
+; Disassembled:
+; block0: ; offset 0x0
+;   saddlp v0.8h, v0.16b
+;   ret
 
 function %fn2(i16x8) -> i32x4 {
 block0(v0: i16x8):
@@ -21,9 +27,15 @@ block0(v0: i16x8):
   return v3
 }
 
+; VCode:
 ; block0:
 ;   saddlp v0.4s, v0.8h
 ;   ret
+; 
+; Disassembled:
+; block0: ; offset 0x0
+;   saddlp v0.4s, v0.8h
+;   ret
 
 function %fn3(i8x16) -> i16x8 {
 block0(v0: i8x16):
@@ -33,9 +45,15 @@ block0(v0: i8x16):
   return v3
 }
 
+; VCode:
 ; block0:
 ;   uaddlp v0.8h, v0.16b
 ;   ret
+; 
+; Disassembled:
+; block0: ; offset 0x0
+;   uaddlp v0.8h, v0.16b
+;   ret
 
 function %fn4(i16x8) -> i32x4 {
 block0(v0: i16x8):
@@ -45,7 +63,13 @@ block0(v0: i16x8):
   return v3
 }
 
+; VCode:
 ; block0:
 ;   uaddlp v0.4s, v0.8h
 ;   ret
+; 
+; Disassembled:
+; block0: ; offset 0x0
+;   uaddlp v0.4s, v0.8h
+;   ret