[STAL-2713] Handle taint propagation in Java for-each loop statement.

[jasonforal]

This is a commit from early September that was unintentionally omitted when slicing the larger taint analysis implementation into smaller PRs.

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What problem are you trying to solve?

Taint isn't propagated between the "item" and "array" of a for-each loop statement:

void method() {
    String[] strings = {\"a\", \"b\", \"c\"};
    String query = \"\";
    for (String s: strings) {
        // `strings` taints `s`, which then taints `query`,
        query += s;
    }
    System.out.println(query);
}

What is your solution?

Add handler for enhanced_for_statement CST nodes.

Alternatives considered

What the reviewer should know