TernaryOperatorsShouldNotBeNested does not handle assignments

TernaryOperatorsShouldNotBeNested is only implemented for return statements and lambdas, not assignments (or other possible places for ternaries).

sample

class Test {
  public void doThing(String a, String b) {
    String result = "a".equals(a) ? "a" : "b".equals(b) ? "b" : "nope";
    System.out.println(result);
  }
}

expected:

class Test {
  public void doThing(String a, String b) {
      String result;
      if ("a".equals(a)) {
        result = "a";
      }
      else {
        result = "b".equals(b) ? "b" : "nope";
      }
      System.out.println(result);
  }
}

actual: no change

Start at the TernaryOperatorsShouldNotBeNested implementation and reproduce the assignment example from the issue. Extend the existing handling so nested ternaries in assignments produce the shown result, then verify that return statements and lambdas remain covered.