Invalid client body encoding results in 500 response, while it should be 4** Error

### Describe the bug
When client sends request with failed encoding 500 Exception is returned, but it's client fault and I believe it should be 400 Bad Request instead.

### To Reproduce
Download solution from https://github.com/sobanieca/AspNetCoreEncodingIssue
Open in Visual Studio
Run WebApplication1 (ensure it listens on localhost:5000)
Run Post-Request.ps1 powershell attached (ensure Powershell ISE working directory is the same as ps1 file, so it can read Request.json file)

### Expected behavior
I would expect API to return 400 Bad Request, as client is sending request with invalid encoding

### Additional context
Inside Post-Request.ps1 script (line 12) one can see fix that client can apply to fix API issue

Exception that is being thrown:
```
fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
An unhandled exception has occurred while executing the request.
System.Text.DecoderFallbackException: Unable to translate bytes [B2] at index 23 from specified code page to Unicode.
at System.Text.DecoderExceptionFallbackBuffer.Throw(Byte[] bytesUnknown, Int32 index)
at System.Text.DecoderExceptionFallbackBuffer.Fallback(Byte[] bytesUnknown, Int32 index)
at System.Text.DecoderFallbackBuffer.InternalFallback(Byte[] bytes, Byte* pBytes, Char*& chars)
at System.Text.UTF8Encoding.GetChars(Byte* bytes, Int32 byteCount, Char* chars, Int32 charCount, DecoderNLS baseDecoder)
at System.Text.DecoderNLS.GetChars(Byte[] bytes, Int32 byteIndex, Int32 byteCount, Char[] chars, Int32 charIndex, Boolean flush)
at System.Text.DecoderNLS.GetChars(Byte[] bytes, Int32 byteIndex, Int32 byteCount, Char[] chars, Int32 charIndex)
at Microsoft.AspNetCore.WebUtilities.HttpRequestStreamReader.ReadIntoBuffer()
at Microsoft.AspNetCore.WebUtilities.HttpRequestStreamReader.Read(Char[] buffer, Int32 index, Int32 count)
at Newtonsoft.Json.JsonTextReader.ReadData(Boolean append, Int32 charsRequired)
at Newtonsoft.Json.JsonTextReader.ParseValue()
at Newtonsoft.Json.JsonTextReader.Read()
at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.AspNetCore.Mvc.Formatters.JsonInputFormatter.ReadRequestBodyAsync(InputFormatterContext context, Encoding encoding)
at Microsoft.AspNetCore.Mvc.ModelBinding.Binders.BodyModelBinder.BindModelAsync(ModelBindingContext bindingContext)
at Microsoft.AspNetCore.Mvc.ModelBinding.ParameterBinder.BindModelAsync(ActionContext actionContext, IModelBinder modelBinder, IValueProvider valueProvider, ParameterDescriptor parameter, ModelMetadata metadata, Object value)
at Microsoft.AspNetCore.Mvc.Internal.ControllerBinderDelegateProvider.<>c__DisplayClass0_0.<g__Bind|0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeInnerFilterAsync()
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter()
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync()
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync()
at Microsoft.AspNetCore.Builder.RouterMiddleware.Invoke(HttpContext httpContext)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
```