Finish [Feature]: Allow custom sounds per sender #991

[guodong323]

[tmolitor-stud-tu]

One more hint: imlement MLSoundManager.m in such a way that MLContact has a field reflecting the sound settings as properties (BOOL chatSoundEnabled and NSString* chatSoundFilename) and automatically refresh these properties by issuing a kMonalContactRefresh and handle this refresh in handleContactRefresh: like already done for the contact avatar.

Use @StateObject ObservableKVOWrapper<MLContact> instead of plain MLContact in swiftui to automatically react to changes of these properties.

[guodong323]

I modify it that user can upload themselves sounds

[guodong323]

I modify it that user can set different alert sound for different users

[guodong323]

I reset the file naming rules, but every time before selecting a new ringtone I delete the previous ringtone file, otherwise the app's memory usage will become high every time I save the file, I hope you'll be satisfied with the solution this time!