RFR (S) 8249822: SymbolPropertyTable creates an extra OopHandle per entry

[coleen . phillimore]

Summary: Add an assert to OopHandle assigment operator to catch leaking 
OopHandles, and fix code accordingly.

There are some jvmtiRedefineClasses.cpp changes here - basically, I 
moved the RedefineVerifyMark and comments into jvmtiRedefineClasses.cpp 
because I needed a Handle.

Ran tier1-6 tests and tier1 on all Oracle platforms.

open webrev at http://cr.openjdk.java.net/~coleenp/2020/8249822.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8249822

Thanks,
Coleen