Introduce base V4 PayloadValidator (#5494)

**Story card:** [sc-14156](URL)

## Because

I'm working on introducing a new sync route and…
- I couldn't find the specs for the validators where they should be
- V4 sync route payload validators were ineriting from a V3 base

## This addresses

- One step towards proper separation of concerns
- Implemeting the same technique for the V3 and V4 sync controllers

## Test instructions

- Ensure existing tests pass since this is purely refactoring

Author: igbanam

app/validators/api/v4/blood_sugar_payload_validator.rb

@@ -1,4 +1,4 @@
-class Api::V4::BloodSugarPayloadValidator < Api::V3::PayloadValidator
+class Api::V4::BloodSugarPayloadValidator < Api::V4::PayloadValidator
   attr_accessor(
     :id,
     :blood_sugar_type,

app/validators/api/v4/call_result_payload_validator.rb

@@ -1,4 +1,4 @@
-class Api::V4::CallResultPayloadValidator < Api::V3::PayloadValidator
+class Api::V4::CallResultPayloadValidator < Api::V4::PayloadValidator
   attr_accessor(
     :id,
     :user_id,

app/validators/api/v4/payload_validator.rb

@@ -0,0 +1,2 @@
+class Api::V4::PayloadValidator < Api::V3::PayloadValidator
+end

app/validators/api/v4/questionnaire_response_payload_validator.rb

@@ -1,4 +1,4 @@
-class Api::V4::QuestionnaireResponsePayloadValidator < Api::V3::PayloadValidator
+class Api::V4::QuestionnaireResponsePayloadValidator < Api::V4::PayloadValidator
   attr_accessor(
     :id,
     :questionnaire_id,

app/validators/api/v4/teleconsultation_payload_validator.rb

@@ -1,4 +1,4 @@
-class Api::V4::TeleconsultationPayloadValidator < Api::V3::PayloadValidator
+class Api::V4::TeleconsultationPayloadValidator < Api::V4::PayloadValidator
   attr_accessor(
     :id,
     :patient_id,