Disable Metal as a default rendering mode for 11.2

[maxkatz6]

What does the pull request do?

For 11.2 we enabled Metal by default on macOS.
But it has several major issues:

• Resizing has poor performance comparing to OpenGL, see Fix window resize jitter with Metal #17415
• Metal rendering backend had a memory leak on resizing, which was already fixed.
• Metal rendering backend has much higher memory consumption on larger window sizes. It's not a leak, as memory is reducing, once window is resized back to smaller sizes.

How was the solution implemented (if it's not obvious)?

Re-enabled OpenGL as a default for 11.2 builds.
Note, this PR targets 11.2 branch directly, and for nightly 11.3 builds we still have metal as default.