If GL_EXT_scalar_block_layout is requested by the shader, set the
option to allow scalar blocks in the SPIR-V validator.
Fix the existing tests using scalar layout to not expect "Validation
failed".
Fixes#2400.
* Changed unit tests to only record known the validation pass/fail
status
* errors are output as part of the failure message if the result is
unexpected
* can turn off validation for each test individually
* Moved some SPV_KHR_vulkan_memory_model tests to be compiled for Vulkan
1.1
