RFR(S) 8241815: Unnecessary calls to SystemDictionaryShared::define_shared_package

[Calvin Cheung]

JBS: https://bugs.openjdk.java.net/browse/JDK-8241815
webrev: http://cr.openjdk.java.net/~ccheung/jdk15/8241815/webrev.00/

This change is to avoid java up call of definePackage() while loading a 
shared app/platform class originated from the module image since the 
packages from module image are already created during  VM bootstrap in 
Module::define_module().

(including core-libs-dev since the change removes two methods in 
jdk/internal/loader/ClassLoaders.java)

Testing: tier1 - 4.

thanks,

Calvin