refactor: split vue and dialogs sub modules to prepare for library splitting

[ShGKme]

• Preparation for [RFC] export of vue components #1809
• Currently @nextcloud/upload has mixed pure API, ui functions (dialogs) and a vue component
  • Also, it has some circular dependencies
• This PR refactors file/module structure:
  • . - pure uploading logic, kept in place
  • dialogs - UI related functions that use Vue only internally and will be moved to @nextcloud/dialogs in the next major
  • vue - exported Vue component (that can only be used in a specific Vue version and will be moved to @nextcloud/vue in the next major)

Before	After

Detailed explanation

Details

[Antreesy]

LGTM

[susnux]

Makes sense in v1.
For v2 we would then need to revert it.

[ShGKme]

For v2 we would then need to revert it.

Why do we need it? The only purpose of the PR is to prepare for v2.
And if we revert, then it's complicated again to move these parts out from the library again.

[susnux]

And if we revert, then it's complicated again to move these parts out from the library again.

Because there will be only the core left.

[ShGKme]

Because there will be only the core left.

I don't understand it in the context of "And if we revert, then it's complicated again to move these parts out from the library again.".

And yes, only the core part is left. That is the purpose of the PR, why is it a problem that requires revert to the mixed state?

With the refactoring there are 3 separated parts. 2/3 can be easily removed, without any changes in the remaining one. Without it, we have mixed modules using each other, including different parts sometimes in a single file.

The only purpose of the PR is to go to v2. If v2 requires reverting the "prepare for v2", when we should close it.

[ShGKme]

Or the only problem is that the "core" as a folder exists without other folders?

If that is the case, we can just move its content to the parent.

[ShGKme]

• Removed core to keep everything from core in root:
  • Then these files have no changes in v2
• Renamed ui to dialogs (goes to the @nextcloud/dialogs)
• Renamed components to vue (goes to the @nextcloud/vue)