preserve order of @Parameters not working for spring-boot 2.2

[ny-currenxie]

The previous fix on #274 works nicely while testing with spring-boot 2.1.x but not working in spring-boot 2.2.

Likely due to the changed annotation handling (https://github.com/spring-projects/spring-framework/wiki/Upgrading-to-Spring-Framework-5.x#upgrading-to-version-52), the method AbstractRequestBuilder.getApiParameters can now only dig out @Parameter annotations in the third call to AnnotatedElementUtils.findAllMergedAnnotations(method, io.swagger.v3.oas.annotations.Parameter.class) even though they are wrapped in @Parameters.

Suggest all 4 Collectors.toMap in the method AbstractRequestBuilder.getApiParameters be changed to collect the results in LinkedHashMap

Sample code:

@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Parameters({
  @Parameter(
      in = ParameterIn.QUERY,
      description = "Page you want to retrieve (0..N)",
      name = "page",
      content = @Content(schema = @Schema(type = "integer", defaultValue = "0"))),
  @Parameter(
      in = ParameterIn.QUERY,
      description = "Number of records per page.",
      name = "size",
      content = @Content(schema = @Schema(type = "integer", defaultValue = "20"))),
  @Parameter(
      in = ParameterIn.QUERY,
      description =
          "Sorting criteria in the format: property(,asc|desc). "
              + "Default sort order is ascending. "
              + "Multiple sort criteria are supported.",
      name = "sort",
      content = @Content(array = @ArraySchema(schema = @Schema(type = "string")))),
  @Parameter(in = ParameterIn.QUERY, name = "pageable", hidden = true),
})
public @interface PageableParameter {}

@PageableParameter
public void someController(Pageable pageable){
   ...
}

Generated api-doc On spring-boot 2.2

 {"name": "size",...},
 {"name": "page",...},
 {"name": "sort",...}

Generated api-doc On spring-boot 2.1.x

 {"name": "page",...},
 {"name": "size",...},
 {"name": "sort",...}

[springdoc]

Hi @ny-currenxie,

Finally, able to reproduce the behaviour you describe.