Fix test failures and add new tests for subscription validation disabling

[RakhithaRR]

This PR fixes the following failing tests due to the addition of new subscription level policies and adds new test cases to cover the subscription validation disabling flows.

• APIM634GetAllTheThrottlingTiersFromThePublisherRestAPITestCase
• APIMGetAllSubscriptionThrottlingPolicies

Related issue: wso2/api-manager#3011

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 18.37%. Comparing base (ebcdd27) to head (cfde468).
Report is 5 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #13527      +/-   ##
============================================
+ Coverage     17.80%   18.37%   +0.56%     
- Complexity      894      929      +35     
============================================
  Files           255      255              
  Lines         11551    11551              
  Branches       1204     1204              
============================================
+ Hits           2057     2122      +65     
+ Misses         9477     9412      -65     
  Partials         17       17              

Flag	Coverage Δ
integration_tests	18.37% <ø> (+0.56%)	⬆️

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