Ability to import animation directly

This MR provides an option to create default Document or image to Import image Sequence over it.

• If there is no active Document and Import Animation is clicked it will add a default size Document to import Image Sequence over it.
• If there is an active Document a checkBox will be shown as a choice to add new Document of default size & resolution .

Otherwise it will import the Image Sequence over the current document if this is not needed.

Bug : https://bugs.kde.org/show_bug.cgi?id=409184

Test Plan

Choose Import Animation from file Menu without any Document and with any Document .

Formalities Checklist

• I confirmed this builds.
• I confirmed Krita ran and the relevant functions work.
• I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
• I made sure my commits build individually and have good descriptions as per KDE guidelines.
• I made sure my code conforms to the standards set in the HACKING file.
• I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.