Add safe-init test to prevent adding cold elements to hot arrays

This adds a negative test to ensure that the initialization checker does
nt allow cold values to be inserted into hot arrays through a method
call.

Author: Xavientois

tests/init/neg/cold-insert-hot-array.scala

@@ -0,0 +1,10 @@
+object A:
+  def foo[T](x: T, array: Array[T]): Unit = array(0) = x
+
+class B {
+  var a = Array.apply(1, 2, 3)
+  A.foo(this.i, a)
+  val i = 99
+}
+
+val b = new B()