RFR: 8292350: Use static methods for hashCode/toString primitives

[Andrey Turbanov]

It's a bit shorter and clearer.

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Commit messages:
 - [PATCH] Use static methods for hashCode/toString primitives

Changes: https://git.openjdk.org/jdk/pull/9816/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9816&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292350
  Stats: 8 lines in 4 files changed: 0 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/9816.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9816/head:pull/9816

PR: https://git.openjdk.org/jdk/pull/9816