RFR: 8065213 Specify and implement PlatformMBeanProvider for looking for all platform MBeans

[shanliang]

Hi,

Please review:

bug: https://bugs.openjdk.java.net/browse/JDK-8065213
webrev:   http://cr.openjdk.java.net/~sjiang/JDK-8065213/00/

The class PlatformMBeanProvider.java is added to allow different modules 
to inform ManagementFactory of their Plaform MBeans. In this version we 
use the ServiceLoader to load these Plaform MBeans, later we will 
replace the ServiceProvider by jigsaw mechanisms.

there are 2 providers in this version:
    DefaultPlatformMBeanProvider: for all MBeans in the 
java.lang.management.* (java.management module)
    com/sun/management/internal/PlatformMBeanProviderImpl: for the 
MBeans in com.sun.management.* com.sun.management.* (jdk.management module)
  
Thanks,
Shanliang