KDropdown and KIconButton tweaks

[nucleogenesis]

Description

• Extend KDropdownButton with a new slot to customize the dropdown options' rendering
• Drill the containFocus prop through KDropdownButton to UiPopover
• Add v-bind="$attrs" to KIconButton
• Add expand/collapse all icons

Issue addressed

This was necessary to accommodate needs for the updates to Kolibri Quiz.

Before/after screenshots

n/a

Steps to test

I suggest testing my Kolibri PR which puts these changes to use.

Testing checklist

• [x] Contributor has fully tested the PR manually
• [ ] The change has been added to the changelog

Reviewer guidance

• [ ] Is the code clean and well-commented?
• [ ] Are there tests for this change?
• [ ] Are all UI components LTR and RTL compliant (if applicable)?

[MisRob]

Please note that release-v1.5.x branch was renamed back to main (part of preparation of the new release and returning back to regular release process after that, more details to come)

[MisRob]

Alright main is ready to be rebased on

[marcellamaki]

@nucleogenesis although I can follow the code changes, I'm a little bit unclear on what exactly you added in the create quiz PR that required this change? Can you explain a little bit? I have it running and also am looking at the code but just wanted to be sure I understand the use case. (Relatedly, adding a sentence or two to the documentation to the same effect would be helpful)

[nucleogenesis]

Hey @marcellamaki I've updated the changelog & docs page to better explain the changes to KDropdownMenu and to offer guidance re: the changes -- thank you for the feedback there I hadn't considered how this would be good to note in the docs 🤦🏻‍♂️

[MisRob]

I'm sorry for being a pain in the butt, but the changelog still needs cleanup, @nucleogenesis. There's still a conflict caused by introducing the new changelog format while this branch was probably in progress already. Could you please remove lines 272-291, and line 294 completely? That's the old format that has already been converted to new items. Let me know if you needed anything.

Your guidance in the new changelog item for this PR looks great, thank you.

[nucleogenesis]

Just a note that I will be splitting this PR into two separate PRs -- one which is necessary specifically for Kolibri work and the other which represents unused changes that were inspired during Kolibri work but went unused. I'll update both changelogs accordingly next week and request re-review from the participants here.

[nucleogenesis]

@marcellamaki @MisRob I've extracted the commits from this PR for the quiz management work into #497 so that these changes appear separately from the others in the changelog.

[MisRob]

@nucleogenesis I am not sure if I could understand the motivation for two pull requests properly. Do you need anything in this one?

[MisRob]

If it's still active and has no breaking updates, please retarget to release-v3 branch before merging.