Dark mode fixes to Pinned Message

[rapterjet2004]

• fixes Dark mode issues with message pinning #5717

• Fixed UI for dark mode
• Moved the Pinned View to it's own file

🖼️ Screenshots

🏚️ Before	🏡 After

🏁 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]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/5737.apk



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

[github-actions]

Codacy

Lint

Type	master	PR
Warnings	99	99
Errors	0	0

SpotBugs

Category	Base	New
Bad practice	6	6
Correctness	10	10
Dodgy code	54	54
Internationalization	3	3
Malicious code vulnerability	3	3
Performance	4	4
Security	1	1
Total	81	81

[AndyScherzinger]

LGTM

[AndyScherzinger]

For further polishing we might want to to make the menu headline bold else it currenrly looks like a menu item without an icon followed by a divider but the time info is not clickable. Else I think it could also be an option to put the time into the pinned message field also.

Not sure what you think of or prefer @nimishavijay

Could well be a follow up of course since it isn't related to the dark mode issue.