Ordering of `GlobalOpenApiCustomizer`s different than for `OpenApiCustomiser`s

[westse]

Describe the bug

The order of injection and execution of user-defined OpenApiCustomiser beans appears to be controllable via the standard Spring means (annotate with @Order or implement org.springframework.core.Ordered). However, this is not true of GlobalOpenApiCustomizer beans which appear to be injected/executed in the order they happened to be defined in the backend configuration. It is particularly confusing when there are multiple beans that implement both interfaces - the order of execution changes depending on whether the api-docs URL used is grouped vs non-grouped.

To Reproduce
Steps to reproduce the behavior:

• Using spring-boot 2.7.6
• Using springdoc-openapi 1.6.14.
• Run the below Spring Boot app
• Open http://localhost:8080/v3/api-docs in a browser
• Observe the console output and notice that customizers are executed in order 1, 2, 3.
• Open http://localhost:8080/v3/api-docs/mygroup in a browser
• Observe the console output and notice that customizers are executed in order 3, 2, 1.

package order;

import io.swagger.v3.oas.models.OpenAPI;
import org.springdoc.core.customizers.GlobalOpenApiCustomizer;
import org.springdoc.core.customizers.OpenApiCustomiser;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Import;
import org.springframework.core.annotation.Order;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@Import({
        OrderDemo.Customizer3.class,
        OrderDemo.Customizer2.class,
        OrderDemo.Customizer1.class,
})
public class OrderDemo {

    @Order(3)
    public static class Customizer3 implements OpenApiCustomiser, GlobalOpenApiCustomizer {
        public void customise(OpenAPI openApi) {
            System.out.println("-> 3");
        }
    }

    @Order(2)
    public static class Customizer2 implements OpenApiCustomiser, GlobalOpenApiCustomizer {
        public void customise(OpenAPI openApi) {
            System.out.println("-> 2");
        }
    }

    @Order(1)
    public static class Customizer1 implements OpenApiCustomiser, GlobalOpenApiCustomizer {
        public void customise(OpenAPI openApi) {
            System.out.println("-> 1");
        }
    }

    @RestController
    public static class MyController {

        @GetMapping("/test")
        public String testingMethod() {
            return "foo";
        }
    }

    public static void main(String[] args) {
        // Ensure at least one group is configured
        System.setProperty("springdoc.group-configs[0].group", "mygroup");
        System.setProperty("springdoc.group-configs[0].paths-to-match", "/test");
        
        SpringApplication.run(OrderDemo.class, args);
    }
}

Expected behavior

• The ordering behavior should be the same for GlobalOpenApiCustomizer and OpenApiCustomiser beans.
• Ideally ordering would be controllable via standard Spring means (e.g. @Order).

Additional Context
I believe this is due to the fact that MultipleOpenApiResource.afterPropertiesSet() (only used for group-configs?) obtains its list of GlobalOpenApiCustomizers via ApplicationContext.getBeansOfType(Class), which is documented to return beans in the "order of the backend configuration", whereas the OpenApiWebResource (used for non-grouped) is autowired and therefore is controllable via standard means (e.g @Order).