RFR: 8284490: Remove finalizer method in java.security.jgss [v8]

[Xue-Lei Andrew Fan]

> Please review the update to remove finalizer method in the java.security.jgss module. It is one of the efforts to clean up the use of finalizer method in JDK.

Xue-Lei Andrew Fan has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 10 commits:

 - Merge and resovle merge conflict
 - change the calling order in dispose()
 - More code cleanup
 - re-org the code per feedback
 - Update to set context method
 - add test cases
 - Merge
 - Update copyright year
 - the object reference issue for Cleaner
 - 8284490: Remove finalizer method in java.security.jgss

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Changes: https://git.openjdk.java.net/jdk/pull/8136/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8136&range=07
  Stats: 219 lines in 9 files changed: 185 ins; 11 del; 23 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8136.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8136/head:pull/8136

PR: https://git.openjdk.java.net/jdk/pull/8136