RFR: 8182621: JSSE should reject empty TLS plaintexts [v2]

[Matthew Donovan]

> Added code similar to the suggested patches for empty Handshake messages. I also implemented tests to verify empty Handshake, Alert, and ChangeCipherSpec messages result in expected behavior: for SSLEngineImpl, exceptions are thrown, for SSLSockets the connection is closed.

Matthew Donovan has updated the pull request incrementally with two additional commits since the last revision:

 - added comment referring to relevant RFC
 - clarified if-statements; fixed exception message wording

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13306/files
  - new: https://git.openjdk.org/jdk/pull/13306/files/92c68e4c..7c47ed30

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13306&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13306&range=00-01

  Stats: 8 lines in 2 files changed: 4 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13306.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13306/head:pull/13306

PR: https://git.openjdk.org/jdk/pull/13306