RFR: 8300979: Lazily initialize (byte, char)arr in java.io.DataInputStream [v4]

[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:

  Use zero-lenght arrays rather than null

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13121/files
  - new: https://git.openjdk.org/jdk/pull/13121/files/efece452..ca165dfa

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13121&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13121&range=02-03

  Stats: 6 lines in 1 file changed: 3 ins; 0 del; 3 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