Add some new String methods in JDK 11 to built-ins mapping blacklist

These three methods are conflicting with existing extensions,
thus the behavior might be changed when switching to JDK 11

Probably, it's worth revisiting our strategy here,
e.g. by blacklisting all new methods in

 #KT-24974 Fixed

compiler/testData/diagnostics/testWithModifiedMockJdk/newStringMethods.kt

@@ -0,0 +1,11 @@
+// !CHECK_TYPE
+// SKIP_TXT
+
+fun foo(s: String) {
+    s.isBlank()
+    s.lines().checkType { _<List<String>>() }
+    s.repeat(1)
+
+    // We don't have `strip` extension, so leave it for a while in gray list
+    s.<!DEPRECATION!>strip<!>()
+}