Ensure path-params rules finds missing parameters

[mehdi-sol]

This PR should solve Issue #435.
Currently, vacuum does not find pick up errors with the two following examples.

Example 1

Details

openapi: 3.0.3
info:
  description: Pizza
  title: Pizza API
  version: 1.0.0
paths:
  /pizza/{type}/{topping}:
    parameters:
      - name: type
        description: Pizza type.
        in: path
        required: true
        schema:
          type: string
    get:
      operationId: get_pizza
      summary: summary
      description: description
      responses:
        '204':
          description: no description

Example 2

Details

openapi: 3.0.3
info:
  description: Pizza
  title: Pizza API
  version: 1.0.0
paths:
  /pizza/{type}/{topping}:
    parameters:
      - name: type
        description: Pizza type.
        in: path
        required: true
        schema:
          type: string
    post:
      parameters:
        - name: topping
          description: Pizza topping.
          in: path
          required: true
          schema:
            type: string
      operationId: make_pizza
      summary: summary
      description: description
      responses:
        '204':
          description: no description

    get:
      operationId: get_pizza
      summary: summary
      description: description
      responses:
        '204':
          description: no description

The first example is failing because `ensureAllExpectedParamsInPathAreDefined` is skipping over `top`. The second example fails because `ensureAllExpectedParamsInPathAreDefined` doesn't take `verb` into account when checking for parameters.

This PR makes sure ensureAllExpectedParamsInPathAreDefined goes over all the expected path parameters and checks both the top-level and the verb-level parameters. I've also added test cases for these scenarios.

[daveshanley]

LGTM! Thank you for your contribution.