RFR: 8276658: Clean up JNI local handles code

[Coleen Phillimore]

JNI Local handles can only be created by JavaThread (there's an assert in make_local) but the fields are added to Thread.
Move the fields to JavaThread and adding JavaThread* argument.
Also, the global freelist isn't very useful now that global JNI handles don't use JNIHandleBlock, so the locking that claims incorrectly to block for safepoint is removed.
Lastly, there's at least 3 places that duplicate pushing a new JNIHandleBlock to the thread for temporarily adding JNI local handles. These have been moved to common code with a JNIHandleMark object, moved from jvmci code.
The commits are separate to help reviewing, but the entire change has been tested together with tier1-6.
The commits in this change have been performance tested individually and together with no meaningful differences from mainline.

-------------

Commit messages:
 - The VM Thread creates handles on the caller thread, unless it runs out then it allocates a block on its own thread, which it never cleans up.  Pass the caller thread to allocate_handle so that allocate_block will add to the right thread, which is a JavaThread.
 - Refactor pushing and popping JNIHandleBlocks.
 - Remove JNIHandleBlock global freelists and Mutex
 - Move active_handles to JavaThread.

Changes: https://git.openjdk.java.net/jdk/pull/6336/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6336&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276658
  Stats: 426 lines in 25 files changed: 77 ins; 302 del; 47 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6336.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6336/head:pull/6336

PR: https://git.openjdk.java.net/jdk/pull/6336