RFR 8215643: Microbenchmarks for KeyAgreement and Cipher

[Adam Petcher]

Webrev: http://cr.openjdk.java.net/~apetcher/8215643/webrev.00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8215643

Please review this enhancement that adds two new crypto microbenchmarks. 
See the JBS ticket for the motivation behind these new benchmarks. The 
Cipher benchmark nearly duplicates some existing AES benchmarks, though 
the measurement is done differently in order to also address 
JDK-8214800[1]. I didn't want to upset anything by removing the existing 
AES benchmarks, but I'm interested in advice on how we should handle 
this duplication.

[1] https://bugs.openjdk.java.net/browse/JDK-8214800