unity vulkan support

• CI: fix build
• build: android build should contain both opengles and vulkan support
• Revert opengl changes or make sure it doesn't break other platforms
• remove or set as debug only some log statements
• add docs for minimum Android API supported for vulkan and possibly unity editor script warning
• add docs on repo/website for Vulkan support
• test on Quest
• see if some unnecessary code written during troubleshooting can be removed (both c# and cpp sides)
• see if we can remove the extra GPU copy (can be done after this MR)
• add runtime fallback to opengl if vulkan is unsupported (can be done after this MR)