'jfr' tool should hide hidden frames

$ jfr print recording.jfr

can result in stack traces with methods that the user has not written, for example:
  
jdk.internal.misc.Unsafe.allocateUninitializedArray
java.lang.invoke.StringConcatFactory$MethodHandleInlineCopyStrategy.newArray
java.lang.invoke.DirectMethodHandle$Holder.invokeStatic
java.lang.invoke.LambdaForm$MH/0x0000000801202440.invoke
java.lang.invoke.LambdaForm$MH/0x0000000801202840.linkToTargetMethod
TestApplication.append1
TestApplication.main

In the recording file, JFR marks these methods as hidden and they should be filtered out.

if users want to see hidden frames, an option (--show-hidden-methods) can be added in a future RFE.