Partial refactor of the mess that is TerminalView

- Decouple the `CursorController`, `TextSelectionCursorController`(previously `SelectionModifierCursorController`) and `TextSelectionHandleView` (previously `HandleView`) from `TerminalView` by moving them to their own class files.
- Fixes #1501 which caused the `java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.` exception to be thrown when long pressing the down key while simultaneously long pressing the terminal view for text selection.

terminal-view/src/main/java/com/termux/view/TerminalRenderer.java

@@ -230,4 +230,12 @@ public final class TerminalRenderer {
 
         if (savedMatrix) canvas.restore();
     }
+
+    public float getFontWidth() {
+        return mFontWidth;
+    }
+
+    public int getFontLineSpacing() {
+        return mFontLineSpacing;
+    }
 }