RFR of JDK-8211975: move testlibrary/jdk/testlibrary/OptimalCapacity.java to top-level library

[Hamlin Li]

Would you please review the following patch?

https://bugs.openjdk.java.net/browse/JDK-8211975

http://cr.openjdk.java.net/~mli/8211975/webrev.00/


Thank you

-Hamlin