KT-2498 Bridge method is not generated for method when generic parameters are substituted in superclass

#KT-2498 Fixed

generateBridgeIfNeeded() now works as follows: for a given method, find
which declared methods does this method override via breadth-first search.
For each such declared method, generate a bridge if and only if its
signature is different. Keep different methods' signatures in a set to
avoid duplicated bridge signatures.

compiler/testData/codegen/regressions/kt2498.kt

@@ -0,0 +1,19 @@
+import java.util.LinkedList
+
+open class BaseStringList: LinkedList<String>() {
+}
+
+class StringList: BaseStringList() {
+    public override fun get(index: Int): String {
+        return "StringList.get()"
+    }
+}
+
+fun box(): String {
+    val myStringList = StringList()
+    myStringList.add("first element")
+    if (myStringList.get(0) != "StringList.get()") return "Fail #1"
+    if ((myStringList: BaseStringList).get(0) != "StringList.get()") return "Fail #2"
+    if ((myStringList: LinkedList<String>).get(0) != "StringList.get()") return "Fail #3"
+    return "OK"
+}