RFR: 8313768: Reduce interaction with volatile field in j.u.l.StreamHandler

[Sergey Tsypanov]

In `publish0()`, `flush0()` and `flushAndClose()`methods of `StreamHandler` we read multiple times from volatile writer. The access number can be reduced by reading the field into local variable once.

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Commit messages:
 - 8313768: Reduce interaction with volatile field in j.u.l.StreamHandler

Changes: https://git.openjdk.org/jdk/pull/15161/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15161&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313768
  Stats: 7 lines in 1 file changed: 6 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15161.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15161/head:pull/15161

PR: https://git.openjdk.org/jdk/pull/15161