<Swing Dev> RFR: 8257809: JNI warnings from Toolkit JPEG image decoding

[Phil Race]

The fix is to reverse the order of acquisition to get dst before src so that the call to GetArrayLength() comes first.
This also necessitates moving the RELEASE_ARRAYS() call on an error condition to the new "2nd" block.

The new regression test passes on all platforms and all the other headless tests passed too.
So do the automated headful tests.

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Commit messages:
 - 8257809: JNI warnings from Toolkit JPEG image decoding
 - 8257809: JNI warnings from Toolkit JPEG image decoding

Changes: https://git.openjdk.java.net/jdk/pull/1850/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1850&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257809
  Stats: 126 lines in 4 files changed: 116 ins; 10 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1850.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1850/head:pull/1850

PR: https://git.openjdk.java.net/jdk/pull/1850