Added special handling for Leaf Constructs

[ammokhov]

Issue #, if available:

Description of changes:

There are certain leaf level constructs - JSON native and CloudFormation specific.

• JSON Native - List of supported constructs
• CloudFormation spcific:
  • arrayType
  • insertionOrder
  • ...

1. Adding constructs to a set of known keywords to be able to include it in the report.
2. Previously it did not check if added nested keyword is a reserved name or not. If it is reserved but we did not check it would be accounted as a property, which is technically not correct.

Example:
previous schema

{
  "properties": {
    "Array": {
      "insertionOrder": true, ...
    }
  }
}

new schema

{
  "properties": {
    "Array": {
      ...
    }
  }
}

original diff:

{
  "properties": {
    "removed": ["/properties/Array/insertionOrder"]
  }
}

new diff:

{
  "insertionOrder": {
    "removed": ["/properties/Array"]
  }
}

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