RFR: 8258754: Gracefully fallback to the OpenGL rendering pipeline if Metal rendering pipeline initialization fails [v6]

[Ajit Ghaisas]

> This implements fallback to the OpenGL rendering pipeline if Metal rendering pipeline initialization fails.
> I have tested this fallback on 10.15.4 by stubbing code. We need real testing on a system where Metal is not available.

Ajit Ghaisas has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments

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Changes:
  - all: https://git.openjdk.java.net/lanai/pull/147/files
  - new: https://git.openjdk.java.net/lanai/pull/147/files/d23bd72f..93ad2318

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=lanai&pr=147&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=lanai&pr=147&range=04-05

  Stats: 119 lines in 7 files changed: 37 ins; 60 del; 22 mod
  Patch: https://git.openjdk.java.net/lanai/pull/147.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/147/head:pull/147

PR: https://git.openjdk.java.net/lanai/pull/147