RFR(S): 8138600: eliminate the need of ModuleLoaderMap.dat for CDS

[Calvin Cheung]

With the fix for JDK-8186842 
<https://bugs.openjdk.java.net/browse/JDK-8186842>, we no longer need 
the ModuleLoaderMap to determine the loader type of a class during CDS 
dump time. This change is for removing the ModuleLoaderMap from the 
runtime image and the code which references it.

bug: https://bugs.openjdk.java.net/browse/JDK-8138600

webrevs:
http://cr.openjdk.java.net/~ccheung/8138600/jdk/webrev.00/
http://cr.openjdk.java.net/~ccheung/8138600/hotspot/webrev.00/

Testing:
     JPRT
     CDS tests
     hs-tier3

thanks,
Calvin