RFR: 8262227: Change SystemDictionary::find() to return an InstanceKlass*.

[Harold Seigel]

Please review this fix for JDK-8262227.  This fix changes SystemDictionary::find() to return an InstanceKlass* to reduce InstanceKlass casts, it renames find() to find_instance_klass(), removes its unneeded TRAP parameter, and changes its callers as appropriate.

It also changed the get_java_...() methods, in thread.cpp, to take an InstanceKlass* parameter and removed their now unneeded TRAPS parameter.

The fix was tested with mach5 tiers 1 and 2 on Linux, Windows, and Mac OS, and tiers 3-5 on Linux x64 (still in progress).

Thanks to Coleen and David for their helpful suggestions.

Thanks, Harold

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

Commit messages:
 - 8262227: Change SystemDictionary::find() to return an InstanceKlass*.

Changes: https://git.openjdk.java.net/jdk/pull/2712/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2712&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262227
  Stats: 90 lines in 13 files changed: 6 ins; 19 del; 65 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2712.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2712/head:pull/2712

PR: https://git.openjdk.java.net/jdk/pull/2712