RFR: 8195972: Refactor oops in JNI to use the Access API

[Kim Barrett]

Please review this change to the JNIHandles class to use the Access
API.  The handle construction, deletion, and value access (via resolve
&etc) are updated to use the Access API.

CR:
https://bugs.openjdk.java.net/browse/JDK-8195972

Webrev:
http://cr.openjdk.java.net/~kbarrett/8195972/open.00/

Testing:
local jck-runtime:vm/jni, tonga:nsk.jvmti
  jtreg:fromTonga_nsk_coverage, jtreg:fromTonga_vm_runtime,
  jtreg/runtime/jni
Mach5 {jdk,hs}-tier{1,2,3}
Mach5 hs-tier{5,6,7}-rt (tiers containing additional JNI tests)