Optimize LineChart area fill rendering to avoid data duplication (#4289)

Refactored `LineChart` to draw filled areas by constructing the `GeneralPath` directly from the source points list, rather than creating a temporary `ArrayList` copy. This reduces memory allocation and garbage collection overhead during chart rendering.
Exposed `AbstractChart.calculateDrawPoints` as protected to facilitate this reuse.
Retained original logic for complex `BOUNDS` fill types where point modification is required.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Author: google-labs-jules[bot]

CodenameOne/src/com/codename1/charts/views/AbstractChart.java

@@ -41,7 +41,7 @@
 public abstract class AbstractChart {
     private static final char[] stopCharCandidates = "!@#$%^&*()?><,./+-qwertyuiop[zxcvbnm,./\\|}{".toCharArray();
 
-    private static float[] calculateDrawPoints(float p1x, float p1y, float p2x, float p2y,
+    protected static float[] calculateDrawPoints(float p1x, float p1y, float p2x, float p2y,
                                                int screenHeight, int screenWidth) {
         float drawP1x;
         float drawP1y;