RFR: 8357714: AudioClip.play crash on macOS when loading resource from jar

[Johan Vos]

After JDK-8287822 (https://bugs.openjdk.org/browse/JDK-8287822), mpeg file content is no longer played via GSTPlatform but via OSXPlatform. 
We need to correctly handle data in case the source is a file inside a jar, in which case CJavaInputStreamCallbacks is used.

The 2 changes I made are:
1. Use ConnectionHolder instead of Locator for CJavaInputStreamCallbacks in case a jar resource is used.
2. In case of random access datasource, use readBlock instead of readNextBlock in AVMediaPlayer

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Commit messages:
 - Use ConnectionHolder instead of Locator for CJavaInputStreamCallbacks

Changes: https://git.openjdk.org/jfx/pull/1839/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1839&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357714
  Stats: 12 lines in 2 files changed: 10 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/1839.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1839/head:pull/1839

PR: https://git.openjdk.org/jfx/pull/1839