RFR: 8242035: Combine drawPrimitive calls in text drawing flush

[Jayathirth D V]

We issue drawPrimitive call per quad in MTLVertexCache.
We can encode all quads present in vertexcache at once.

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Commit messages:
 - 8242035: Combine drawPrimitive calls in text drawing flush

Changes: https://git.openjdk.java.net/lanai/pull/19/files
 Webrev: https://webrevs.openjdk.java.net/lanai/19/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8242035
  Stats: 8 lines in 1 file changed: 0 ins; 2 del; 6 mod
  Patch: https://git.openjdk.java.net/lanai/pull/19.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/19/head:pull/19

PR: https://git.openjdk.java.net/lanai/pull/19