ContextAnalysis: Track local variables and function parameters separately.

This enables us to add all local variable Definitions to the DAST so that downstream visitors don't need to compute the local variables of a function again.

src/test/java/DestroyStatementTest.java

@@ -17,6 +17,6 @@ public class DestroyStatementTest {
         ContextAnalysis ctxAnal = new ContextAnalysis(funcs, structs, enums);
         
         Exception e = assertThrows(RuntimeException.class, () -> ctxAnal.visit(tree));
-        assertEquals("Error in line 1:45 Variable with name \"x\" not defined.", e.getMessage());
+        assertEquals("Error in line 1:45 Variable or parameter with name \"x\" not defined.", e.getMessage());
     }
 }