feat: Merge plugin modules (#10895)

Fixes: FRMW-2858

This PR merge the modules exported by the plugins with the modules defined within the user config. As a result, all modules get loaded without changing the internals of the loader.

However, you cannot disable the module of a plugin by re-adding it to the `modules` array. That is something we should handle separately. 

We've added the breaking change label because of the following fix:
We did broke the ability to completely disable modules in the past pr's, in this pr we re add the ability to disable a module and that this modules does not get loaded at all. ([here](6dd164f783))

Co-authored-by: Adrien de Peretti <25098370+adrien2p@users.noreply.github.com>

packages/core/modules-sdk/src/medusa-app.ts

@@ -106,7 +106,8 @@ export async function loadModules(args: {
     let declaration: any = {}
     let definition: Partial<ModuleDefinition> | undefined = undefined
 
-    if (mod === false) {
+    // TODO: We are keeping mod === false for backward compatibility for now
+    if (mod === false || (isObject(mod) && "disable" in mod && mod.disable)) {
       continue
     }