[OpenJDK 2D-Dev] RFR: 8265304: Temporarily make Metal the default 2D rendering pipeline for macOS

[Ajit Ghaisas]

This PR makes Metal as the default Java2D rendering pipeline for macOS.

Note : from JBS description :
The plan of record has always been that for JDK 17 the new Metal pipeline will be OFF by default and must be explicitly enabled by setting a system property.
We are not changing that plan but to get more testing exposure we intend to make it the default (instead of OpenGL) for approximately one month (from the next build up to the 20th May build of JDK 17).

-------------

Commit messages:
 - 8265304 - make metal pipeline default

Changes: https://git.openjdk.java.net/jdk/pull/3534/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3534&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265304
  Stats: 7 lines in 1 file changed: 3 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3534.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3534/head:pull/3534

PR: https://git.openjdk.java.net/jdk/pull/3534