RFR: 8296787: Unify debug printing format of X.509 cert serial numbers

[Ben Perez]

Updated `X509CertSelector.java` and `SerialNumber.java` to use same debug printing format for X.509 serial numbers. The format in `SSLLogger.java` is slightly different but now uses the `toString` method in `SerialNumber.java` for better readability.

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Commit messages:
 - Merge branch 'openjdk:master' into JDK-8296787
 - Changed SSLLogger to print x509 serial number using toString method in SerialNumber.java
 - Standardized x509 serial number format for X509CertSelector and SerialNumber

Changes: https://git.openjdk.org/jdk/pull/16834/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16834&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296787
  Stats: 6 lines in 3 files changed: 0 ins; 3 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/16834.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16834/head:pull/16834

PR: https://git.openjdk.org/jdk/pull/16834