fix(app-vite&webpack): properly resolve AE script paths

[yusufkandemir]

What kind of change does this PR introduce?

• Bugfix

Does this PR introduce a breaking change?

• No

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)

Other information:
Supersedes #17795

• use / instead of join for import paths:
  • import('quasar-app-extension-foo\\dist\\index.js') is not valid. join uses the separate according to the OS
  • similar to how getPackageJson is implemented without using join
• packagePath = (... || getPackageScriptPath(...)) would end up .../pkg-path/dist/index.js, so this.#packagePath was sometimes pointing out to src/dist, rather than the package root.
  • this.#packagePath no longer exists, so this no longer needs to be fixed with resolve(..., '..')
• always use appDir when resolving AE scripts
• add code comments to clarify the behavior

[DouglasCalora]

I tested linking localy (quasar ext invoke) on projects:

• app-vite v2: worked ✅
• app-webpack v4: worked ✅

app-webpack v3 will no longer be supported?

Thanks for the efford!

[yusufkandemir]

Thanks for confirming. I am hoping for another confirmation, especially from someone using Windows.

app-vite v1 and app-webpack v3 are legacy now, we won't be making more updates to them.

[eliasassuncao]

I also tested linking locally (quasar ext invoke) on Windows with the following projects:

• app-vite v2: worked ✅
• app-webpack v4: worked ✅

Thanks for the support!

[DouglasCalora]

Note: I did not tested this by adding extension without linkin it localy.

On app-webpack v3, I just changed to this code:

    return getPackageScriptPath(
      this.packageFullName,
      scriptName,
      appPaths.appDir
    )

And worked the link.