Prevent sticker picker from being opened in incompatible situations

[hackerbirds]

The sticker picker could be opened when the user is about to send an attachment, or a reply, or text, neither of which can be combined with stickers.

I have personally witnessed many users thinking they could reply to a message with a sticker, then be surprised when the sticker they sent does not include the reply. This change makes it clear that you cannot send stickers as a reply to a message, or with text/attachments. Note that this behavior follows what iOS is doing, and I think Android should do the same.

First time contributor checklist:

• [X] I have read the README and Contributor Guidelines
• [X] I have signed the Contributor Licence Agreement

Contributor checklist:

• [X] My contribution is not related to translations.
• [X] My commits are in nice logical chunks with good commit messages
• [X] My changes are rebased on the latest main branch
• [X] A npm run ready run passes successfully (more about tests here)
• [X] My changes are ready to be shipped to users

Description