[new rule]: The body parameter in patch operation should not be nullable

### Lint rule description

The body parameter in patch operation should not be nullable, check this https://github.com/Azure/autorest.csharp/issues/1968 for more information.

### Related swagger example

N

### Category

SDK

### Severity level

Warning

### Applies to

Management plane API spec, Data plane API spec

### How to fix the violation

Mark it as required, "required": true

### What't the impact if breaking the rule

Usage issue