GL_ARB_enhanced_layouts: mind double types

GL_ARB_enhanced_layouts: mind double types

Double precision types have specific restrictions and rules regarding
the use of the "component" layout qualifier. This change tests those
rules.

Additionally, since the new test is more generic and covers several
cases of the varying_exceeding_components test, simplified the latter.

Components: OpenGL

VK-GL-CTS issue: 725

Affects:

KHR-GL44.enhanced_layouts.varying_array_components
KHR-GL44.enhanced_layouts.varying_component_of_invalid_type
KHR-GL44.enhanced_layouts.varying_components
KHR-GL44.enhanced_layouts.varying_exceeding_components
KHR-GL44.enhanced_layouts.varying_invalid_value_component

Change-Id: Ie20a768b3002f82a1205db338b20ee28b58380f1