RFR (T) 8250042: Clean up methodOop and method_oop names from the code

[coleen.phillimore at oracle.com]

See bug for more details.  I've been running into these names a lot 
lately.   Many of these names are in JVMTI.

Tested with tier1 on all Oracle platforms and built on non-Oracle platforms.

open webrev at http://cr.openjdk.java.net/~coleenp/2020/8250042.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8250042

Thanks,
Coleen