capture conversion: ensure captured wildcards are not replaced after creation, so substitution is consistent; at the same time ensure that "?" with upper bound Runnable is equivalent to "? extends Runnable"

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting/IDEA57533.java

@@ -1,6 +1,6 @@
 class C<T extends C<? extends C<? extends T>>>{
     void foo(C<?> x){
-        <error descr="Inferred type 'capture<? extends C<? extends C<capture<?>>>>' for type parameter 'T' is not within its bound; should extend 'C<capture<? extends C<? extends C<capture<?>>>>>'">bar(x)</error>;
+        <error descr="Inferred type 'capture<?>' for type parameter 'T' is not within its bound; should extend 'C<capture<?>>'">bar(x)</error>;
     }
     <T extends C<? extends T>> void bar(C<T> x){}
 }