[android] Unify custom map server dialog logic and UI

- Add setting icon for custom map server download option.
- Extract shared custom map server dialog helper.
- Clean up based on reviewers' feedback.

Signed-off-by: NoelClick <dev@noel.click>

android/sdk/src/main/java/app/organicmaps/sdk/Framework.java

@@ -356,14 +356,16 @@ public class Framework
 
   public static void applyCustomMapDownloadUrl(@NonNull Context context, @Nullable String url)
   {
-    String normalizedUrl = url != null ? url.trim() : "";
-
-    // Normalize
-    if (!normalizedUrl.isEmpty() && !normalizedUrl.endsWith("/"))
-      normalizedUrl = normalizedUrl + "/";
-
-    nativeSetCustomMapDownloadUrl(normalizedUrl);
+    nativeSetCustomMapDownloadUrl(normalizeServerUrl(url));
     // Reset the legacy downloader too (world/coasts).
     app.organicmaps.sdk.DownloadResourcesLegacyActivity.nativeResetMetaConfig();
   }
+
+  public static String normalizeServerUrl(@Nullable String url)
+  {
+    String out = url != null ? url.trim() : "";
+    if (!out.isEmpty() && !out.endsWith("/"))
+      out = out + "/";
+    return out;
+  }
 }

android/sdk/src/main/java/app/organicmaps/sdk/OrganicMaps.java

@@ -2,12 +2,13 @@ package app.organicmaps.sdk;
 
 import android.content.Context;
 import android.content.SharedPreferences;
-import android.preference.PreferenceManager;
 
 import androidx.annotation.NonNull;
 import androidx.lifecycle.DefaultLifecycleObserver;
 import androidx.lifecycle.LifecycleOwner;
 import androidx.lifecycle.ProcessLifecycleOwner;
+import androidx.preference.PreferenceManager;
+
 import app.organicmaps.sdk.bookmarks.data.BookmarkManager;
 import app.organicmaps.sdk.bookmarks.data.Icon;
 import app.organicmaps.sdk.downloader.Android7RootCertificateWorkaround;
@@ -27,6 +28,7 @@ import app.organicmaps.sdk.util.SharedPropertiesUtils;
 import app.organicmaps.sdk.util.StorageUtils;
 import app.organicmaps.sdk.util.log.Logger;
 import app.organicmaps.sdk.util.log.LogsManager;
+
 import java.io.IOException;
 
 public final class OrganicMaps implements DefaultLifecycleObserver