RFR: 8241234: Unify monitor enter/exit runtime entries

[Yudi Zheng]

Hello,

Please review this patch that unifies the monitor enter/exit runtime entries used by C1, C2, and JVMCI.

https://bugs.openjdk.java.net/browse/JDK-8061553 added support for faster "slow" locking paths. 
These paths are not currently used by JVMCI (or C1) leading to slower performance on programs 
that have a lot of short lived locked sections (such as dacapo:h2). 

This patch creates helper methods based on C2’s monitor enter/exit entries, and shares with the C1, 
JVMCI runtimes. It will prevent these runtimes from missing future updates.

https://bugs.openjdk.java.net/browse/JDK-8241234
http://cr.openjdk.java.net/~yzheng/8241234/webrev.00/

Many thanks,
Yudi