RFR(L): 8242088: Replace mutually exclusive lists with concurrent alternatives

[Markus Gronlund]

Greetings,

Please review the following enhancement:

Enh / bug: https://bugs.openjdk.java.net/browse/JDK-8242088 
Webrev: http://cr.openjdk.java.net/~mgronlun/8242088/webrev/ 
Testing: jdk_jfr, stress tests

Much of this change set provides a foundation for https://bugs.openjdk.java.net/browse/JDK-8233705, about to be sent separately.

Thank you
Markus