bug: parameter allowEmptyValue + required interactions (via #5142)

* add failing tests
* standardize parameter keying
* validateParam test migrations
* migrate test cases to new pattern
* disambiguate name/in ordering in `body.body` test cases
* `name+in`=> `{in}.{name}`
* consider allowEmptyValue parameter inclusion in runtime validation
* use config object for all validateParam options
* drop isXml flag from validateParams

test/e2e-cypress/static/documents/bugs/5129.yaml

@@ -0,0 +1,26 @@
+openapi: "3.0.0"
+
+paths:
+  /aev:
+    get:
+      parameters: 
+      - name: param
+        in: query
+        allowEmptyValue: true
+        schema:
+          type: string
+      responses:
+        200:
+          description: ok
+  /aev/and/required:
+    get:
+      parameters:
+      - name: param
+        in: query
+        allowEmptyValue: true
+        required: true
+        schema:
+          type: string
+      responses:
+        200:
+          description: ok