Cleanup element call and UI (#4641)

* Use ElementTheme.colors.bgCanvasDefault instead of MaterialTheme.colorScheme.background

Even if the value is the same, we should use color from ElementTheme.

* Remove background management of ElementCallActivity. It does not work as expected and also changing theme during a call would require to load the url again with the new theme.

* Do not use isSystemInDarkTheme() directly.

* Use bgSubtleSecondary for background color of Preview.

* Use default colors for Preview.

* Fix copy paste issue.

* Update screenshots

---------

Co-authored-by: ElementBot <android@element.io>

features/call/impl/src/main/kotlin/io/element/android/features/call/impl/ui/ElementCallActivity.kt

@@ -10,7 +10,6 @@ package io.element.android.features.call.impl.ui
 import android.Manifest
 import android.app.PictureInPictureParams
 import android.content.Intent
-import android.content.res.Configuration
 import android.media.AudioAttributes
 import android.media.AudioFocusRequest
 import android.media.AudioManager
@@ -78,7 +77,6 @@ class ElementCallActivity :
 
     private val requestPermissionsLauncher = registerPermissionResultLauncher()
 
-    private var isDarkMode = false
     private val webViewTarget = mutableStateOf<CallType?>(null)
 
     private var eventSink: ((CallScreenEvents) -> Unit)? = null
@@ -102,10 +100,6 @@ class ElementCallActivity :
             return
         }
 
-        if (savedInstanceState == null) {
-            updateUiMode(resources.configuration)
-        }
-
         pictureInPicturePresenter.setPipView(this)
 
         audioManager = getSystemService(AUDIO_SERVICE) as AudioManager
@@ -174,11 +168,6 @@ class ElementCallActivity :
         }
     }
 
-    override fun onConfigurationChanged(newConfig: Configuration) {
-        super.onConfigurationChanged(newConfig)
-        updateUiMode(newConfig)
-    }
-
     override fun onNewIntent(intent: Intent) {
         super.onNewIntent(intent)
         setCallType(intent)
@@ -283,19 +272,6 @@ class ElementCallActivity :
         }
     }
 
-    private fun updateUiMode(configuration: Configuration) {
-        val prevDarkMode = isDarkMode
-        val currentNightMode = configuration.uiMode and Configuration.UI_MODE_NIGHT_YES
-        isDarkMode = currentNightMode != 0
-        if (prevDarkMode != isDarkMode) {
-            if (isDarkMode) {
-                window.setBackgroundDrawableResource(android.R.drawable.screen_background_dark)
-            } else {
-                window.setBackgroundDrawableResource(android.R.drawable.screen_background_light)
-            }
-        }
-    }
-
     @RequiresApi(Build.VERSION_CODES.O)
     override fun setPipParams() {
         setPictureInPictureParams(getPictureInPictureParams())