Reverts "[Impeller] hash even less stuff per frame. (#55092)"

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Reverts: #55092

Initiated by: jonahwilliams

Reason for reverting: framework golden failures.

Original PR Author: jonahwilliams

Reviewed By: {chinmaygarde, jtmcdole}

This change reverts the following previous change:
Follow up to #55060

Currently we have multiple stages of hashing while font rendering, which is relatively expensive for the actualy required workload. First, we hash the contents of all text frames to compute the unique set of glyphs per frame. Then we diff this hash set against the hashmap of glyphs within the atlas. Finally we hash and lookup the final rendered bounds for each glyph.

We can simplify this to 2. hash lookups for glyphs not yet in the atlas and 1. hash lookup for glyphs that are in the atlas. This is done by combing the step where we uniquely compute glyphs per frame with the diff against the current atlas. When this lookup is performed, we also store the glyph position (if found) in the text_frame itself - which allows text contents to skip the last hash, as long as the glyph has already been rendered.

Before

After

Using this handy dandy test app:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {

  Widget build(context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Platform View'),
        ),
        body: SafeArea(child: Stack(children: [
          SizedBox(
            width: 380,
            height: 380,
            child: LinearProgressIndicator(),
          ),
          Stack(
            children: List<Widget>.generate(1000, (index) {
              // The problem already happens with a small amount of widgets.
              // Using an excessive amount of widgets is just to make the problem more evident.
              return Text("Lots of Texts represent a Widget with complex components.");
            }),
          ),

          Align(
            alignment: Alignment.bottomCenter,
            child:
            TextButton(
              child: Text("Button"),
              onPressed: () {
                print("Tap ${DateTime.now()}");
              },
            ),
          ),
        ],
        ),
        ),
      ),
    );
  }
}