RFA: CSR: 8231593 : Add a command line option to control notification mechanism.

[Daniil Titov]

Please review/approve a CSR  request.

The proposed CSR [1] is for adding  a new VM option UseNotificationThread  (default true) to opt-out from
the new behavior introduced by the suggested fix [3] for the issue [2]  that is on review now in the separate 
email thread [4].

 [1] CSR: https://bugs.openjdk.java.net/browse/JDK-8231593 
 [2] Issue: https://bugs.openjdk.java.net/browse/JDK-8170299 
 [3] http://cr.openjdk.java.net/~dtitov/8170299 
 [4]  https://mail.openjdk.java.net/pipermail/serviceability-dev/2019-October/029397.html 

Thank you,
Daniil