Error messages printing

• Adds better error messages.
• Removes a lot of errors that were either not being used, or could be replaced by another exception.

src/main/main_errors/expect_tests/main_errors_test.ml

@@ -305,14 +305,15 @@ error (`Concrete_pascaligo_unsupported_pattern_type pvar) ;
   [%expect
     {|
   in file "a dummy file name", line 20, characters 0-10
-  Argument a dummy file name:20:0-10: String "yolo"
-   of foo must be a string singleton
+  Invalid "foo" type.
+  At this point, an annotation, in the form of a string, is expected for the preceding type.
   |}] ;
   error (`Concrete_pascaligo_michelson_type_wrong_arity (location_t, "zzz")) ;
   [%expect
     {|
       in file "a dummy file name", line 20, characters 0-10
-      zzz does not have the right number of argument|}] ;
+      Invalid "zzz" type.
+      An even number of 2 or more arguments is expected, where each odd item is a type annotated by the following string.|}] ;
   error
     (`Concrete_pascaligo_instruction_tracer
       ( Skip default_region1,
@@ -322,7 +323,8 @@ error (`Concrete_pascaligo_unsupported_pattern_type pvar) ;
   in file "a dummy file name", line 20, characters 0-10
   Abstracting instruction:@"a dummy file name:20:0-10: skip
   "@in file "a dummy file name", line 20, characters 0-10
-  zzz does not have the right number of argument
+  Invalid "zzz" type.
+  An even number of 2 or more arguments is expected, where each odd item is a type annotated by the following string.
   |}] ;
   error
     (`Concrete_pascaligo_program_tracer
@@ -332,7 +334,8 @@ error (`Concrete_pascaligo_unsupported_pattern_type pvar) ;
     {|
   in file "a dummy file name", line 20, characters 0-10
   Abstracting program@in file "a dummy file name", line 20, characters 0-10
-  zzz does not have the right number of argument
+  Invalid "zzz" type.
+  An even number of 2 or more arguments is expected, where each odd item is a type annotated by the following string.
   |}] ;
   error (`Concrete_pascaligo_recursive_fun location_t) ;
   [%expect