[BUG] [aspnetcore] Problem when using several identical schemas in request

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

The swagger UI is not accessible, due to 3 similar object types in the test method
public virtual IActionResult TestPost(IFormFile bin, [FromForm]Vec3 location, [FromForm]Vec3 roation, [FromForm]Vec3 scale)

The resulting error:
`Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware: Error: An unhandled exception has occurred while executing the request.

System.ArgumentException: An item with the same key has already been added. Key: X
at System.Collections.Generic.Dictionary'2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateSchemaFromFormParameters(IEnumerable'1 formParameters, SchemaRepository schemaRepository)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateRequestBodyFromFormParameters(ApiDescription apiDescription, SchemaRepository schemaRepository, IEnumerable'1 formParameters)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateRequestBody(ApiDescription apiDescription, SchemaRepository schemaRepository)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateOperation(ApiDescription apiDescription, SchemaRepository schemaRepository)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateOperations(IEnumerable'1 apiDescriptions, SchemaRepository schemaRepository)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GeneratePaths(IEnumerable'1 apiDescriptions, SchemaRepository schemaRepository)
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GetSwagger(String documentName, String host, String basePath)
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)`

openapi-generator version

5.1.1 and tested with 5.2.0 snapshot from 29.06

OpenAPI declaration file content or url

https://gist.github.com/tschumacher93/9abcf1ddbc839eddbc804cd5f9760efb

Generation Details

I just used the following command to generate the server files:
java -jar ..\openapi-generator-cli.jar generate -i ..\openapi.json -g aspnetcore -o .

Steps to reproduce

1.) Generate code
2.) Adjust Startup.cs and Program.cs, so that the restapi is runnable
3.) open swagger page

Related issues/PRs

Suggest a fix

Start by reproducing the generated aspnetcore project from the linked OpenAPI declaration with the stated Java CLI command, then inspect Startup.cs, Program.cs, and the Swagger page. Trace the duplicate-key exception from Swashbuckle's GenerateSchemaFromFormParameters for the three Vec3 form parameters. Done means the Swagger page loads without this exception for the reported endpoint.