RFR: 8313087: DerValue::toString should output the values in byte array

[John Jiang]

DerValue::toString may be better to output the hex view of the byte array variable `buffer`.

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Commit messages:
 - 8313087: DerValue::toString should output the values in byte array

Changes: https://git.openjdk.org/jdk/pull/15029/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15029&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313087
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15029.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15029/head:pull/15029

PR: https://git.openjdk.org/jdk/pull/15029