RFR: 8305157: The java.util.Arrays class should be declared final

[Per Minborg]

Non-instantiable utility classes should be declared `final` and have a private constructors. 

See Effective Java, Third Edition, Joshua Bloch (for example, Item 19 or Item 22).

-------------

Commit messages:
 - Make java.util.Arrays final

Changes: https://git.openjdk.org/jdk/pull/13221/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13221&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305157
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13221.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13221/head:pull/13221

PR: https://git.openjdk.org/jdk/pull/13221