RFR: 8261851: update ReflectionCallerCacheTest.java test to use ForceGC from test library

[Mandy Chung]

Update test/jdk/java/lang/reflect/callerCache/ReflectionCallerCacheTest.java to use ForceGC from test library which has additional instrumentation to diagnose problem.   In addition, this will get the fix for JDK-8258007.

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Commit messages:
 - fix copyright header update
 - update copyright header
 - 8261851: update test to use ForceGC from test library

Changes: https://git.openjdk.java.net/jdk/pull/2597/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2597&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261851
  Stats: 39 lines in 1 file changed: 1 ins; 37 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2597.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2597/head:pull/2597

PR: https://git.openjdk.java.net/jdk/pull/2597