Review Request 8238195: Lookup::defineClass should link the class to match the specification

[Mandy Chung]

The spec of `Lookup::defineClass` specifies to throw linkage error 
including `VerifyError` and JDK-8238358 fixes the implementation to 
match the spec [1].

This patch updates the spec to make it clear as proposed in the 
CSR:https://bugs.openjdk.java.net/browse/JDK-8240338.  Also add a new 
test case to verify that `defineClass` does link a class.

Webrev at:
http://cr.openjdk.java.net/~mchung/jdk15/webrevs/8238195/webrev.00/

Thanks
Mandy
[1] 
https://mail.openjdk.java.net/pipermail/core-libs-dev/2020-March/065456.html