fix: Medusa service base method transaction (#7758)

**What**
Remove transaction decorator from the base medusa service method, the transaction will always be coming from the shared context. It fixes the issue that when you consume a base method directly it will return a proper tuple from the DB instead of the one from the entity map cc @VariableVic 

**NOTE**
This pr also fix some categories issues in the product module which was preventing the tests from working. if @sradevski you could have a look later, in the mean time we can still merge it

FIXES CORE-2342

packages/modules/product/integration-tests/__tests__/product-category.ts

@@ -1015,7 +1015,7 @@ moduleIntegrationTestRunner<Service>({
           }
 
           expect(error.message).toEqual(
-            `ProductCategory not found ({ id: 'does-not-exist' })`
+            `ProductCategory with id: does-not-exist was not found`
           )
         })
 
@@ -1162,7 +1162,7 @@ moduleIntegrationTestRunner<Service>({
           }
 
           expect(error.message).toEqual(
-            `ProductCategory not found ({ id: 'does-not-exist' })`
+            `ProductCategory with id: does-not-exist was not found`
           )
         })
 

packages/modules/product/integration-tests/__tests__/product-module-service/product-categories.spec.ts

@@ -565,7 +565,7 @@ moduleIntegrationTestRunner<IProductModuleService>({
           }
 
           expect(error.message).toEqual(
-            `ProductCategory not found ({ id: 'does-not-exist' })`
+            `ProductCategory with id: does-not-exist was not found`
           )
         })