Fix Diagnostic Positions

[rcosta358]

This PR fixes the target locations of some errors and warnings:

• All errors except for refinement and state refinement errors now correctly target the predicates that caused them
• The non-existent class warning now targets the qualified name of the class that we are trying to refine

Examples

Before

Warning: Could not find class 'non.existent.Class'
...
5 | @ExternalRefinementsFor("non.existent.Class")
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
6 | public interface NonExistentClass {
...


State Conflict Error: Found multiple disjoint states in state transition: state transition can only go to one state of each state set
...
12 |     @StateRefinement(from="open(this) && closed(this)")
13 |     public void close() {}
   |                 ^^^^^^^^^^
...

Not Found Error: Variable 'x' not found
...
 8 |         @Refinement("x > 0")
 9 |         int y = 1;
   |             ^^^^^^
...

Syntax Error: Invalid refinement expression, expected a logical predicate
...
 8 |         @Refinement("x $ 0")
   |         ^^^^^^^^^^^^^^^^^^^^
 9 |         int x = -1;
...

After

Warning: Could not find class 'non.existent.Class'
...
5 | @ExternalRefinementsFor("non.existent.Class")
  |                         ^^^^^^^^^^^^^^^^^^^^
6 | public interface NonExistentClass {
...

State Conflict Error: Found multiple disjoint states in state transition: state transition can only go to one state of each state set
...
12 |     @StateRefinement(from="open(this) && closed(this)")
   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
13 |     public void close() {}
...

Not Found Error: Variable 'x' not found
...
 8 |         @Refinement("x > 0")
   |                     ^^^^^^^
 9 |         int y = 1;
...

Syntax Error: Invalid refinement expression, expected a logical predicate
...
 8 |         @Refinement("x $ 0")
   |                     ^^^^^^^
 9 |         int x = -1;
...

---

Before merging into main, and after #177 has been merged into main, this branch should be updated with improve-test-suite to ensure proper testing.