glsl/shader_cache: Save fs (BlendSupport) metadata

glsl/shader_cache: Save fs (BlendSupport) metadata

Fixes many GL 4.5 CTS blend tests, such as:

* GL45-CTS.blend_equation_advanced.extension_directive_enable
* GL45-CTS.blend_equation_advanced.extension_directive_warn
* GL45-CTS.blend_equation_advanced.blend_all.GL_MULTIPLY_KHR_all_qualifier
* GL45-CTS.blend_equation_advanced.blend_specific.GL_COLORBURN_KHR

v2:
 * Directly save the BlendSupport field to avoid potentially including
   a pointer in the future in the structure is updated. (tarceri)

Cc: Timothy Arceri <tarceri@itsqueeze.com>
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>