F3017: unhelpful error message

I got this error message:

```
«ValidationFailed» core/test/cfn-resource.test.ts:68:2
WARNING Value is not valid under any of the given schemas for AWS::EC2::Volume (CloudFormation Validate)
TestStack/Resource (Resource) constructs.Construct
Acknowledge with 'CloudFormation-Validate::F3017'
```

For the following resource definition:

```js
{
Resource: {
Type: "AWS::EC2::Volume",
}
}
```

I think it is complaining about an absent or empty `Properties` dictionary. Now, it's not *wrong* to say that `Valid is not valid under any of the given schemas`... but it's also not a very helpful error message either. Something about "required properties missing" would have been a more helpful message.

Start with core/test/cfn-resource.test.ts:68 and reproduce the AWS::EC2::Volume validation case with no Properties dictionary. Trace the validation diagnostic from that test and make the resulting warning explain that required properties are missing; the test should demonstrate the more helpful wording.

Written by the indexing model from the issue text.