v1.124

v1.124:

HIGHLIGHTS:

• dropped "mGPU" support (minor breaking change)
• improved VK performance

DETAILS:

• dropped "mGPU" support, which was incomplete in VK, was not implemented in D3D12
• added missing VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT flag
• VK: minor improvements
• resolved some TODOs
• refactoring