Changed|Deprecated: Deprecate use-black-ui termux property and replace it with night-mode

This will not break existing `use-black-ui` settings for users and it will automatically be converted to `night-mode` when properties are loaded from disk but a deprecation message will be logged.

This `night-mode` key can be used to set the day/night theme variant for activities used by termux app and its plugin. The user can set a string value to `true` to force use dark variant of theme, `false` to force use light variant of theme or `system` to automatically set theme based on current system settings. The default value is still `system`. The app must be restarted for changes to take effect for existing activities, including main terminal `TermuxActivity`.

This is required since "theme != night mode". In future custom theme or color support may be provided that will have both dark and night modes for the same theme.

termux-shared/src/main/java/com/termux/shared/theme/ThemeUtils.java

@@ -0,0 +1,33 @@
+package com.termux.shared.theme;
+
+import android.content.Context;
+import android.content.res.Configuration;
+
+import com.termux.shared.models.theme.NightMode;
+
+public class ThemeUtils {
+
+    /**
+     * Will return true if system has enabled night mode.
+     * https://developer.android.com/guide/topics/resources/providing-resources#NightQualifier
+     */
+    public static boolean isNightModeEnabled(Context context) {
+        if (context == null) return false;
+        return (context.getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK) == Configuration.UI_MODE_NIGHT_YES;
+
+    }
+
+    /** Will return true if mode is set to {@link NightMode#TRUE}, otherwise will return true if
+     * mode is set to {@link NightMode#SYSTEM} and night mode is enabled by system. */
+    public static boolean shouldEnableDarkTheme(Context context, String name) {
+        if (NightMode.TRUE.getName().equals(name))
+            return true;
+        else if (NightMode.FALSE.getName().equals(name))
+            return false;
+        else if (NightMode.SYSTEM.getName().equals(name)) {
+            return isNightModeEnabled(context);
+        } else {
+            return false;
+        }
+    }
+}