fix: load custom modules by path (#6312)

What:
medusa-config.js loading custom modules by their path.

```typescript
{
  modules: {
    internalModule: {
      scope: MODULE_SCOPE.INTERNAL,
      resources: MODULE_RESOURCE_TYPE.SHARED,
      resolve: "./internal_module",
      definition: {
        key: "internalModule",
        registrationName: "internalModule",
      },
    },
  }
}
```

packages/modules-sdk/src/loaders/__tests__/register-modules.ts

@@ -18,7 +18,6 @@ describe("module definitions loader", () => {
     label: "TestService",
     isLegacy: true,
     isRequired: false,
-    canOverride: true,
     defaultModuleDeclaration: {
       scope: MODULE_SCOPE.INTERNAL,
       resources: MODULE_RESOURCE_TYPE.SHARED,

packages/modules-sdk/src/loaders/register-modules.ts

@@ -94,7 +94,7 @@ function getInternalModuleResolution(
 
   // If user added a module and it's overridable, we resolve that instead
   const isString = typeof moduleConfig === "string"
-  if (definition.canOverride && (isString || (isObj && moduleConfig.resolve))) {
+  if (isString || (isObj && moduleConfig.resolve)) {
     resolutionPath = !moduleExports
       ? resolveCwd(isString ? moduleConfig : (moduleConfig.resolve as string))
       : // Explicitly assign an empty string, later, we will check if the value is exactly false.

packages/modules-sdk/src/loaders/utils/load-internal.ts

@@ -29,12 +29,12 @@ export async function loadInternalModule(
     // the exports. This is useful when a package export an initialize function which will bootstrap itself and therefore
     // does not need to import the package that is currently being loaded as it would create a
     // circular reference.
-    const path = resolution.resolutionPath as string
+    const modulePath = resolution.resolutionPath as string
 
     if (resolution.moduleExports) {
       loadedModule = resolution.moduleExports
     } else {
-      loadedModule = await import(path)
+      loadedModule = await import(modulePath)
       loadedModule = (loadedModule as any).default
     }
   } catch (error) {