Matan Lurey 91526aaded [Impeller] Add gradient dithering for Radial/Sweep/Conical gradients (flutter/engine#44331) ...

Partial work towards https://github.com/flutter/flutter/issues/131450
similar to https://github.com/flutter/engine/pull/44181.

---

Run the Playground locally:

```bash
$ENGINE/out/host_debug_unopt/impeller_unittests \
  --enable_playground \
  --gtest_filter="*CanRender*GradientWithDithering*"
```

## Radial

### Before

<img width="1014" alt="Screenshot 2023-08-03 at 10 08 53 AM"
src="https://github.com/flutter/engine/assets/168174/d53f2c0e-5c48-4ecb-8e67-d4ab28bfe488">

### After

<img width="1018" alt="Screenshot 2023-08-03 at 10 13 57 AM"
src="https://github.com/flutter/engine/assets/168174/3b6e6e65-3dd3-4cb3-9950-36e2ba5c1da2">

## Sweep

### Before

<img width="1019" alt="Screenshot 2023-08-03 at 10 27 35 AM"
src="https://github.com/flutter/engine/assets/168174/4e3bc82d-c0d5-43dd-952a-c11cb586fb65">

### After

<img width="1018" alt="Screenshot 2023-08-03 at 10 33 11 AM"
src="https://github.com/flutter/engine/assets/168174/7e526391-cfd7-4920-89ff-fe26793b24fc"

## Conical

### Before

<img width="1019" alt="Screenshot 2023-08-08 at 11 55 43 AM"
src="https://github.com/flutter/engine/assets/168174/944709f4-8163-4de3-bfc5-eaf30b978529">

### After

<img width="1016" alt="Screenshot 2023-08-08 at 1 11 40 PM"
src="https://github.com/flutter/engine/assets/168174/60ad67a4-b409-4136-a753-b8608f46fbf2">

2023-08-08 16:23:38 -07:00

..

src/flutter

[Impeller] Add gradient dithering for Radial/Sweep/Conical gradients (flutter/engine#44331)

2023-08-08 16:23:38 -07:00