fix(files_sharing): select sharing in sidebar breaks Viewer focus trap

[ShGKme]

• Resolves: [BITV]: Focus trap on search field doesn't work well #39434

Summary

• Actually, this is a revert of: Fix share select dropdown not opening when viewer is open #36998

What's happening in the mentioned PR:

1. User opens select
2. SharingInput emits global event viewer:trapElements:changed sending the NcSelect instance
3. Viewer handles this event and adds this NcSelect instance to the @nextcloud/vue/NcModal additional trap elements

Why there was a problem:

Each time a select is open, a global event triggers viewer which then adds this select as additionalTrapElement. As the result:

1. 10 times opened select adds 10 selects to additional trap elements
2. select becomes a new tabbableGroup which is supposed to be already a part of sidebar group.

On first open it works fine. On the second and following it breaks. When a user is in the open select again and presses TAB the following happens:

1. focus-trap searches the first tabbableGroup with select
2. Then searches for the next element in this group (nothing found). Then search for the next tabbableGroup
3. Next tabbableGroup is the a group with select again.
4. focus-trap focuses the same select again.

See also: https://github.com/focus-trap/focus-trap/blob/c68a1ca87f2dfd905d9f97b91e2d0318268b5ea3/index.js#L529-L535

Why the fix from the mentioned PR is not needed now:

It is fixed globally by nextcloud-libraries/nextcloud-vue#4406 (see: nextcloud-libraries/nextcloud-vue@f6a6de1).

When additionalTrapElements are taken into account on init, select works as a part of the sidebar which is already added into additionalTrapElements.

TODO

• Remove emitting viewer:trapElements:changed on each sharing select open in sidebar

Screenshots

Before	After
Tab forward gets stuck on select	Tab forward goes forward
Tab backward ends on select	Tab backward goes backward

Alternative or additional solution

In NcModal or/and Viewer we can check that there are no duplications in additionalTrapElements.

Folowing-up

There is still a problem with a focus on "Copy internal link button". Not related to this PR, but could be a related problem...

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[Pytal]

🤯