core: faster tracking of active subscriptions; ui: only track in foreground (#4446)

* core: faster tracking of active subscriptions

* combine db transaction

* optimizations of queries from UI

* ios: track when active

* ios: disable log

---------

Co-authored-by: Avently <7953703+avently@users.noreply.github.com>
Co-authored-by: spaced4ndy <8711996+spaced4ndy@users.noreply.github.com>

apps/multiplatform/common/src/androidMain/kotlin/chat/simplex/common/platform/AppCommon.android.kt

@@ -6,8 +6,6 @@ import android.net.LocalServerSocket
 import android.util.Log
 import androidx.activity.ComponentActivity
 import androidx.fragment.app.FragmentActivity
-import chat.simplex.common.*
-import chat.simplex.common.platform.*
 import java.io.*
 import java.lang.ref.WeakReference
 import java.util.*
@@ -24,6 +22,8 @@ var isAppOnForeground: Boolean = false
 @Suppress("ConstantLocale")
 val defaultLocale: Locale = Locale.getDefault()
 
+actual fun isAppVisibleAndFocused(): Boolean = isAppOnForeground
+
 @SuppressLint("StaticFieldLeak")
 lateinit var androidAppContext: Context
 var mainActivity: WeakReference<FragmentActivity> = WeakReference(null)