RFR: 8300979: Lazily initialize (byte, char)arr in java.io.DataInputStream [v2]

[Per Minborg]

> This PR proposed to lazily initialize the scratch arrays only if/when needed.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Update src/java.base/share/classes/java/io/DataInputStream.java
  
  Co-authored-by: Eirik Bjorsnos <eirbjo at gmail.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13121/files
  - new: https://git.openjdk.org/jdk/pull/13121/files/9d99127b..d689e36b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13121&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13121&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13121.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13121/head:pull/13121

PR: https://git.openjdk.org/jdk/pull/13121