[Vulkan video] Duplicated frames cause a black screen

Description

Sending duplicated frames from the cores cause a black screen.
When using the Vulkan driver in RetroArch, frame duping can result in a
black screen until the next input that causes a new frame to be
rendered. This happens when RetroArch does a video driver reinit. For
example when switching RetroArch from fullscreen to windowed or vice
versa. Or when the core requests a reinit through
RETRO_ENVIRONMENT_SET_SYSTEM_AV_INFO.

Expected behavior

Sending duplicate frames with the Vulkan driver, or doing a video driver reinit, Retroarch should show the content on screen, just like with the GL driver.

Actual behavior

Sending duplicate frames with the Vulkan driver, or doing a video driver reinit, Retroarch shows a black screen until a new frame is sent.

Steps to reproduce the bug

Happens on both beetle-psx and dosbox-core when frame-dupping is enable.
So, for example on the dosbox-core core with the Vulkan driver set as video driver:

1. Load the dosbox-core core
2. Load SuperFrog
3. You will be on a black screen until you enter a value or press a key that causes a new different frame to be sent.

Bisect Results

In theory it has always happened with the Vulkan driver. Does not happen with the GL driver.

Version/Commit

You can find this information under Information/System Information

• RetroArch: 1.9.14 stable, and also current GIT code.

Environment information

• OS: GNU/Linux (X11, KMSDRM, Wayland)
• Compiler: gcc version 10.2.1 (Debian 10.2.1-6)

Related bugs

https://github.com/realnc/dosbox-core/issues/36

Reproduce the issue with dosbox-core, SuperFrog, frame duplication, and the Vulkan video driver, then compare the behavior with the GL driver. Start by tracing video reinitialization through RETRO_ENVIRONMENT_SET_SYSTEM_AV_INFO and the duplicated-frame path. Done means duplicated frames remain visible after a Vulkan video-driver reinit without waiting for a new frame.