RFR: 8308010: X509Key and PKCS8Key allows garbage bytes at the end

[Weijun Wang]

When parsing a byte array to a private or public key, it's now converted to a `ByteArrayInputStream` and the parser does not report an error if there are extra bytes at the end.

-------------

Commit messages:
 - the fix

Changes: https://git.openjdk.org/jdk/pull/13958/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13958&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308010
  Stats: 80 lines in 3 files changed: 62 ins; 9 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/13958.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13958/head:pull/13958

PR: https://git.openjdk.org/jdk/pull/13958