Tidyup varfont_shader_puzzle (#1629)

* Tidyup `varfont_shader_puzzle`

* Add a rebuild script and a test

* Simplify fragment shaders

* Drop web

* Enable `beta` CI

* make it `beta` inclusive

* Pull out the program loading code

experimental/varfont_shader_puzzle/lib/page_content/page_ascender_descender.dart

@@ -200,7 +200,7 @@ class _PageAscenderDescenderState extends SinglePageState {
       pageConfig: widget.pageConfig,
       numTiles: 9,
       puzzleNum: 3,
-      shaderKey: 'row_offset',
+      shader: Shader.rowOffset,
       shaderDuration: 2000,
       tileShadedString: 'fyd',
       tileShadedStringPadding: EdgeInsets.only(

experimental/varfont_shader_puzzle/lib/page_content/page_narrative_post.dart

@@ -1,6 +1,7 @@
 // Copyright 2023 The Flutter team. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 import 'package:flutter/material.dart';
 import '../components/components.dart';
 import '../page_content/pages_flow.dart';

experimental/varfont_shader_puzzle/lib/page_content/page_narrative_pre.dart

@@ -1,6 +1,7 @@
 // Copyright 2023 The Flutter team. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 import 'package:flutter/material.dart';
 import '../components/components.dart';
 import '../page_content/pages_flow.dart';

experimental/varfont_shader_puzzle/lib/page_content/page_optical_size.dart

@@ -1,6 +1,7 @@
 // Copyright 2023 The Flutter team. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 import 'dart:math';
 
 import 'package:flutter/material.dart';
@@ -178,7 +179,7 @@ class _PageOpticalSizeState extends SinglePageState {
       pageConfig: widget.pageConfig,
       numTiles: 16,
       puzzleNum: 4,
-      shaderKey: 'wavy',
+      shader: Shader.wavy,
       shaderDuration: 5000,
       tileShadedString: 'Z',
       tileShadedStringPadding:

experimental/varfont_shader_puzzle/lib/page_content/page_weight.dart

@@ -1,6 +1,7 @@
 // Copyright 2023 The Flutter team. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 import 'dart:math';
 
 import 'package:flutter/material.dart';
@@ -168,7 +169,7 @@ class _PageWeightState extends SinglePageState {
       pageConfig: widget.pageConfig,
       numTiles: 9,
       puzzleNum: 1,
-      shaderKey: 'wavy2',
+      shader: Shader.wavy2,
       shaderDuration: 3000,
       tileShadedString: 'W',
       tileShadedStringPadding: EdgeInsets.only(

experimental/varfont_shader_puzzle/lib/page_content/page_width.dart

@@ -1,6 +1,7 @@
 // Copyright 2023 The Flutter team. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 import 'dart:math';
 
 import 'package:flutter/material.dart';
@@ -203,7 +204,7 @@ class _PageWidthState extends SinglePageState {
       pageConfig: widget.pageConfig,
       numTiles: 16,
       puzzleNum: 2,
-      shaderKey: 'bw_split',
+      shader: Shader.bwSplit,
       shaderDuration: 2000,
       tileShadedString: 'S',
       tileShadedStringPadding: EdgeInsets.only(

experimental/varfont_shader_puzzle/lib/page_content/pages.dart

@@ -1,6 +1,7 @@
 // Copyright 2023 The Flutter team. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 export 'page_ascender_descender.dart';
 export 'page_narrative_post.dart';
 export 'page_narrative_pre.dart';

experimental/varfont_shader_puzzle/lib/page_content/pages_flow.dart

@@ -1,6 +1,7 @@
 // Copyright 2023 The Flutter team. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 import 'dart:math';
 
 import 'package:flutter/material.dart';

experimental/varfont_shader_puzzle/lib/page_content/wallpapers_flow.dart

@@ -1,6 +1,7 @@
 // Copyright 2023 The Flutter team. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';