Chore/rm main entity concept (#7709)

**What**
Update the `MedusaService` class, factory and types to remove the concept of main modules. The idea being that all method will be explicitly named and suffixes to represent the object you are trying to manipulate.
This pr also includes various fixes in different modules

Co-authored-by: Stevche Radevski <4820812+sradevski@users.noreply.github.com>
Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

integration-tests/modules/__tests__/fulfillment/fulfillment.workflows.spec.ts

@@ -48,7 +48,7 @@ medusaIntegrationTestRunner({
               type: "default",
             })
 
-            const fulfillmentSet = await service.create({
+            const fulfillmentSet = await service.createFulfillmentSets({
               name: "test",
               type: "test-type",
             })
@@ -111,7 +111,7 @@ medusaIntegrationTestRunner({
               type: "default",
             })
 
-            const fulfillmentSet = await service.create({
+            const fulfillmentSet = await service.createFulfillmentSets({
               name: "test",
               type: "test-type",
             })
@@ -190,7 +190,7 @@ medusaIntegrationTestRunner({
               type: "default",
             })
 
-            const fulfillmentSet = await service.create({
+            const fulfillmentSet = await service.createFulfillmentSets({
               name: "test",
               type: "test-type",
             })

integration-tests/modules/__tests__/fulfillment/index.spec.ts

@@ -40,7 +40,7 @@ medusaIntegrationTestRunner({
       it("should allow to create a full data structure after the backward compatible migration have run on top of the medusa v1 database", async () => {
         await setupFullDataFulfillmentStructure(service, { providerId })
 
-        const fulfillmentSets = await service.list(
+        const fulfillmentSets = await service.listFulfillmentSets(
           {},
           {
             relations: [
@@ -119,7 +119,7 @@ medusaIntegrationTestRunner({
           type: "default",
         })
 
-        const fulfillmentSet = await service.create({
+        const fulfillmentSet = await service.createFulfillmentSets({
           name: "test",
           type: "test-type",
         })