Make ShaderMaterial always the last option in inspector resource dropdowns

ShaderMaterial is the "advanced" option, while the "basic" options
should be listed first for easier accessibility (and because they're
generally used more often).

This makes sky and particle materials consistent with
canvas/spatial/fog materials on this aspect.

misc/extension_api_validation/4.2-stable.expected

@@ -73,3 +73,12 @@ GH-87668
 Validate extension JSON: Error: Field 'classes/Font/methods/find_variation/arguments': size changed value in new API, from 8 to 9.
 
 Added optional "baseline_offset" argument. Compatibility method registered.
+
+
+GH-81996
+--------
+Validate extension JSON: Error: Field 'classes/GPUParticles2D/properties/process_material': type changed value in new API, from "ShaderMaterial,ParticleProcessMaterial" to "ParticleProcessMaterial,ShaderMaterial".
+Validate extension JSON: Error: Field 'classes/GPUParticles3D/properties/process_material': type changed value in new API, from "ShaderMaterial,ParticleProcessMaterial" to "ParticleProcessMaterial,ShaderMaterial".
+Validate extension JSON: Error: Field 'classes/Sky/properties/sky_material': type changed value in new API, from "ShaderMaterial,PanoramaSkyMaterial,ProceduralSkyMaterial,PhysicalSkyMaterial" to "PanoramaSkyMaterial,ProceduralSkyMaterial,PhysicalSkyMaterial,ShaderMaterial".
+
+Property hints reordered to improve editor usability. The types allowed are still the same as before. No adjustments should be necessary.

scene/2d/gpu_particles_2d.cpp

@@ -817,7 +817,7 @@ void GPUParticles2D::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "amount", PROPERTY_HINT_RANGE, "1,1000000,1,exp"), "set_amount", "get_amount");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "amount_ratio", PROPERTY_HINT_RANGE, "0,1,0.0001"), "set_amount_ratio", "get_amount_ratio");
 	ADD_PROPERTY(PropertyInfo(Variant::NODE_PATH, "sub_emitter", PROPERTY_HINT_NODE_PATH_VALID_TYPES, "GPUParticles2D"), "set_sub_emitter", "get_sub_emitter");
-	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "process_material", PROPERTY_HINT_RESOURCE_TYPE, "ShaderMaterial,ParticleProcessMaterial"), "set_process_material", "get_process_material");
+	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "process_material", PROPERTY_HINT_RESOURCE_TYPE, "ParticleProcessMaterial,ShaderMaterial"), "set_process_material", "get_process_material");
 	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "texture", PROPERTY_HINT_RESOURCE_TYPE, "Texture2D"), "set_texture", "get_texture");
 	ADD_GROUP("Time", "");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "lifetime", PROPERTY_HINT_RANGE, "0.01,600.0,0.01,or_greater,suffix:s"), "set_lifetime", "get_lifetime");

scene/3d/gpu_particles_3d.cpp

@@ -764,7 +764,7 @@ void GPUParticles3D::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "trail_enabled"), "set_trail_enabled", "is_trail_enabled");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "trail_lifetime", PROPERTY_HINT_RANGE, "0.01,10,0.01,or_greater,suffix:s"), "set_trail_lifetime", "get_trail_lifetime");
 	ADD_GROUP("Process Material", "");
-	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "process_material", PROPERTY_HINT_RESOURCE_TYPE, "ShaderMaterial,ParticleProcessMaterial"), "set_process_material", "get_process_material");
+	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "process_material", PROPERTY_HINT_RESOURCE_TYPE, "ParticleProcessMaterial,ShaderMaterial"), "set_process_material", "get_process_material");
 	ADD_GROUP("Draw Passes", "draw_");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "draw_passes", PROPERTY_HINT_RANGE, "0," + itos(MAX_DRAW_PASSES) + ",1"), "set_draw_passes", "get_draw_passes");
 	for (int i = 0; i < MAX_DRAW_PASSES; i++) {

scene/resources/sky.cpp

@@ -82,7 +82,7 @@ void Sky::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_material", "material"), &Sky::set_material);
 	ClassDB::bind_method(D_METHOD("get_material"), &Sky::get_material);
 
-	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "sky_material", PROPERTY_HINT_RESOURCE_TYPE, "ShaderMaterial,PanoramaSkyMaterial,ProceduralSkyMaterial,PhysicalSkyMaterial"), "set_material", "get_material");
+	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "sky_material", PROPERTY_HINT_RESOURCE_TYPE, "PanoramaSkyMaterial,ProceduralSkyMaterial,PhysicalSkyMaterial,ShaderMaterial"), "set_material", "get_material");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "process_mode", PROPERTY_HINT_ENUM, "Automatic,High-Quality,High-Quality Incremental,Real-Time"), "set_process_mode", "get_process_mode");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "radiance_size", PROPERTY_HINT_ENUM, "32,64,128,256,512,1024,2048"), "set_radiance_size", "get_radiance_size");