Use explicit modifer in export-import test case

[jxzgithub]

According to the spec of drm modifier, the imported image should be created with explicit modifier with subresource layouts and other information provided by the application. However, the current code base doesn't use explicit modifiers in the 'test exportImportMemoryExplicitModifiersCase'. As a result, the paths around VK_STRUCTURE_TYPE_IMAGE_DRM_FORMAT_MODIFIER_EXPLICIT_CREATE_INFO_EXT in an implementation are not covered as intended.

CC: @llandwerlin-intel @nchery-intel

[CLAassistant]

All committers have signed the CLA.

[lordalcol]

These two commits are already merged in the main branch as https://github.com/KhronosGroup/VK-GL-CTS/commit/64478a26f43ecf474ec7d7cfd80b5cd13fee09b4 and https://github.com/KhronosGroup/VK-GL-CTS/commit/166d5f65c0136f3bed9c98706a65d314f299b5ca