[jdk13u-dev] RFR: 8259535: ECDSA SignatureValue do not always have the specified length

[Yuri Nesterenko]

the same backport as in 11u and 15u, with only difference from the original in test printout formatting around line 91.

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Commit messages:
 - Backport a4c249610e7c0fcc7fd863f14f51c96abc5ca39f

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/315/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=315&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259535
  Stats: 232 lines in 4 files changed: 221 ins; 2 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/315.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/315/head:pull/315

PR: https://git.openjdk.java.net/jdk13u-dev/pull/315