Fix to open conversation list when navigating back

[mahibi]

Fix to open conversation list when navigating back after chat was opened by notification

fix #2959 which was when working on #1551

created #2961 to migrate away from onBackPressed

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔖 Capability is checked or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

[github-actions]

Codacy

Lint

Type	master	PR
Warnings	109	109
Errors	0	0

SpotBugs

Category	Base	New
Correctness	9	9
Dodgy code	163	163
Internationalization	5	5
Malicious code vulnerability	3	3
Performance	11	11
Security	2	2
Total	193	193

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/2960-talk.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud Talk app.

[mahibi]

If somehow this solution turns out to be problematic, another approach can be to use the TaskStackBuilder:

https://developer.android.com/reference/androidx/core/app/TaskStackBuilder

https://stackoverflow.com/questions/36912325/why-do-we-use-the-taskstackbuilder