RFR: 8251468: X509Certificate.get{Subject, Issuer}AlternativeNames does not throw CertificateParsingException if extension is unparseable

[Sean Mullan]

The JDK implementation (as supplied by the "SUN" provider) of `X509Certificate::getSubjectAlternativeNames` and `X509Certificate::getIssuerAlternativeNames` returns `null` instead of throwing a `CertificateParsingException` when the extension is unparseable.

This fix changes the behavior to comply with the specification.

CSR: https://bugs.openjdk.java.net/browse/JDK-8275822

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Commit messages:
 - Remove trailing whitespace.
 - 8251468: X509Certificate.get{Subject,Issuer}AlternativeNames does not throw CertificateParsingException if extension is unparseable

Changes: https://git.openjdk.java.net/jdk/pull/6106/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6106&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8251468
  Stats: 199 lines in 4 files changed: 157 ins; 33 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6106.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6106/head:pull/6106

PR: https://git.openjdk.java.net/jdk/pull/6106