Fix Instance Variable Leak Between Methods

[rcosta358]

Description

Fixes #270.
Prevents instance variables from leaking between sibling methods by clearing them before checking a new method/constructor.

Example

int fibonacci(@Refinement("_ > 0") int n) {
    if (n == 1)
        return 1;
    else
        return fibonacci(n - 1) + fibonacci(n - 2); // Refinement Error
}

int factorial(@Refinement("_ > 0") int n) {
    return n * factorial(n - 1); // Refinement Error
}

Both invalid recursive calls are now reported.

Related Issue

#270.

Type of change

• Bug fix
• New feature
• Documentation update
• Code refactoring

Checklist

• Added/updated tests under liquidjava-example/src/main/java/testSuite/ (Correct* / Error*)
• mvn test passes locally
• Updated docs/README if behavior or API changed