feat: get stickers out of nerd mode

[r10s]

currently, when opening the sticker selector, one is pointed to some deeply nested folder, where one shall create "subfolder" and do things there.

this is nothing we want the average user to understand. it also tends to be dangerous, as ppl can easily mess up things in that folder, deleting profiles accidentally etc.

it is okay if a nerd knows about the structure, but we do not want to push user into that.

as we recently added a sticker selector on android as well, instead, we want to have a more consistent way about doing things. this means as a first step:

• when tapping a sticker ask directly if it shall be added to the collection (ask_add_sticker_to_collection), the context menu can stay as is for now
• replace hint about folders and subfolders (add_stickers_instructions) with the hint "Tap a sticker to add it here." (sticker_picker_empty_hint)
• remove all buttons with "open sticker folder" (open_sticker_folder)
• add the option "Delete" to the stickers context menu, the confirmation dialog can use ask_delete_sticker

once we have that, android and desktop stickers handling is consistent, and we can think about adding options to handle groups (which may be subfolders, sure, but we do not want to expose that)

this issue is low-prio, cmp #6193

cc @adbenitez

[nicodh]

Shouldn't we at least have a dialog for importing sticker packs via a zip file import? Otherwise there are only the few stickers available that "others" send...

[r10s]

Shouldn't we at least have a dialog for importing sticker packs via a zip file import? Otherwise there are only the few stickers available that "others" send...

yes. this is planned. also to ship some stickers with the app. but details are not yet clear, so not directly actionable. but first we want to have a common ground. and the "folder" features are definitely unwanted, and very likely not used by anyone but nerds - who can continue to add stickers that way.