GS: Improve vsync mode selection

[stenzek]

Description of Changes

All games use mailbox/triple buffering. Except when you enable sync to host refresh, in which case FIFO/double buffering is used.

This means vsync enabled will ever tear, but at the same time, never drop to 30fps on a missed frame due to frame rate differences. Unless you're using OpenGL, because that doesn't support triple buffering, in which case, too bad.

To have the "best of both worlds", you should enable vsync and sync to host refresh. Previously, this resulted in additional input lag, since the host vsync would drive the EE frame timing. Now, this behaviour is disabled by default, unless you enable "Use Host VSync Timing".

Rationale behind Changes

Trying to make both stutter-wanters and tear-wanters happy.

Suggested Testing Steps

Hammer vsync options.