fix(NewMessage): limit 'set cursor to the end' to editing

[Antreesy]

☑️ Resolves

• Fix regression from fix(NewMessage): set cursor to the end when focus #16152
  • Cursor was also set when briefly unfocus tab / bring from background
  • Now only limited to editing messages, as per original issue

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🚧 Tasks

• Need manual testing
• Probably feat(NcRichContenteditable): put caret in the end when focus input nextcloud-libraries/nextcloud-vue#4924 might interfere on Linux, but not Windows (Firefox and Chrome)

🏁 Checklist

• 🌏 Tested with different browsers / clients:
  • Chromium (Chrome / Edge / Opera / Brave)
  • Firefox
  • Safari
  • Talk Desktop
  • Integrations with Files sidebar and other apps
  • Not risky to browser differences / client
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

[nickvergessen]

Doesn't seem to be the actual problem at the moment, but it's actually
nextcloud-libraries/nextcloud-vue@0dceb6b

We are checking details, at least the problem I have is reproducable on https://nextcloud-vue-components.netlify.app/#/Components/NcRichContenteditable

[Antreesy]

Probably nextcloud-libraries/nextcloud-vue#7791 should fix original issue on Linux. This PR still might be helpful with focusing window

[Antreesy]

/backport to stable32

[Antreesy]

/backport to stable31