RFR: 8245693: Lanai: [_MTLCommandEncoder dealloc]:70: failed assertion `Co…

[Alexey Ushakov]

…mmand encoder released without endEncoding'

Create encoder in [MTLLayer blitTexture] to allow asynchronous processing in metal

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Commit messages:
 - 8245693: Lanai: [_MTLCommandEncoder dealloc]:70: failed assertion `Command encoder released without endEncoding'

Changes: https://git.openjdk.java.net/lanai/pull/46/files
 Webrev: https://webrevs.openjdk.java.net/lanai/46/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8245693
  Stats: 15 lines in 2 files changed: 2 ins; 11 del; 2 mod
  Patch: https://git.openjdk.java.net/lanai/pull/46.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/46/head:pull/46

PR: https://git.openjdk.java.net/lanai/pull/46