Log Vulkan loader errors if the instance failed creation on Fuchsia
The vulkan loader can output logs to help us debug why instance creation
fails. To catch these logs, we need to pass a debug report callback to
vkCreateInstance (since the only other debug report callback is set up
after the instance is created).
Outputting logs is currently only enabled on Fuchsia, since other
platforms may have fallbacks and wouldn't want the error logspam.
Fixes https://github.com/flutter/flutter/issues/82928
*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*
[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
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