RFR: 8258661: Inner class ResponseCacheEntry could be static

[Xue-Lei Andrew Fan]

The inner class StatusResponseManager#ResponseCacheEntry could be static, for better performance.

Code cleanup, no new regression test.

Bug: https://bugs.openjdk.java.net/browse/JDK-8258661

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Commit messages:
 - 8258661: Inner class ResponseCacheEntry could be static

Changes: https://git.openjdk.java.net/jdk/pull/1838/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1838&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258661
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1838.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1838/head:pull/1838

PR: https://git.openjdk.java.net/jdk/pull/1838