glsl: restrict consumer stage condition to modify interpolation type

glsl: restrict consumer stage condition to modify interpolation type

Only modify interpolation type for integer-based varyings or when the
consumer is known and different than fragment shader.

If we are linking separate shader programs and the consumer is unknown,
the consumer could be added later and be a fragment shader. If we
modify the interpolation type in this case, we could read wrong
values in the fragment shader inputs, as shown in bug 93320.

Fixes the following CTS test:
   ES31-CTS.vertex_attrib_binding.advanced-bindingUpdate

Fixes the following dEQP tests:

dEQP-GLES31.functional.separate_shader.random.102
dEQP-GLES31.functional.separate_shader.random.111
dEQP-GLES31.functional.separate_shader.random.115
dEQP-GLES31.functional.separate_shader.random.17
dEQP-GLES31.functional.separate_shader.random.22
dEQP-GLES31.functional.separate_shader.random.23
dEQP-GLES31.functional.separate_shader.random.3
dEQP-GLES31.functional.separate_shader.random.32
dEQP-GLES31.functional.separate_shader.random.39
dEQP-GLES31.functional.separate_shader.random.64
dEQP-GLES31.functional.separate_shader.random.73
dEQP-GLES31.functional.separate_shader.random.91

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93320
Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>