RFR(XS): 8065050: vm crashes during CDS dump when very small SharedMiscDataSize is specified

[Calvin Cheung]

JBS: https://bugs.openjdk.java.net/browse/JDK-8065050

Adding more checks on the SharedMiscDataSize, ShareReadOnlySize, and 
SharedReadWriteSize.

For the SharedMiscDataSize, it is based on 
MetaspaceShared::generate_vtable_methods(). Similar to what was done for 
the SharedMiscCodeSize.

For the ShareReadOnlySize and SharedReadWriteSize, I'm checking if they 
are at least the default size.
I think it's reasonable to enforce the ro and rw sizes to be at least 
the default size. A default dump of CDS archive requires >8M of ro space 
and >11M of rw space.

webrev:
     http://cr.openjdk.java.net/~ccheung/8065050/webrev/

tests:
     ran the testcase via jtreg on linux_x64 and windows_x64
     JPRT

thanks,
Calvin