chore: Remove deprecated flame_oxygen package (#3947)

Removes the deprecated `flame_oxygen` bridge package and its traces from
the repository:

- Deletes `packages/flame_oxygen` (including its example app) and
removes both of its workspace
  entries from the root `pubspec.yaml`.
- Deletes the `flame_oxygen` bridge package docs page and its entries in
`doc/bridge_packages/bridge_packages.md`, plus the `flame_oxygen` bullet
and links in the
  root `README.md`.
- Replaces the Oxygen docs (`doc/other_modules/oxygen`) with a single
page stating that Oxygen
and `flame_oxygen` are deprecated, no longer maintained, and not
recommended, and that the
  Flame Component System is as efficient in almost all cases.
- Removes the `OxygenGame` node from the low-level game API diagram.

The historical `flame_oxygen` entries in the root `CHANGELOG.md` are
left untouched, since that
file records the release history. Already published versions of
`flame_oxygen` remain available
on pub.dev.

## Testing instructions

- Run `flutter pub get` in the repo root and verify that the workspace
still resolves.
- Run `grep -ri oxygen . --exclude-dir=.git --exclude=CHANGELOG.md` and
verify that the only
remaining references are the deprecation notice in `doc/other_modules`.
- Build the docs and verify that the "Other Modules" section renders the
Oxygen deprecation page
  and that the bridge packages page no longer lists `flame_oxygen`.

Author: spydon

.github/.cspell/flame_dictionary.txt

@@ -7,7 +7,6 @@ Bodymovin # An After Effects extension to export Lottie animations https://aescr
 Dashbook # UI development tool for Flutter https://github.com/bluefireteam/dashbook
 emberquest # Ember Quest, our platformer tutorial game
 Hermione # A character from the book Harry Potter
-Kawabunga # Word expressing exhilaration, of unclear origins but popularized by the show Teenage Mutant Ninja Turtles
 Kenobi # Eminent Jedi Master, General of the Republic Army, Obi-Wan Kenobi
 Nakama # An open-source server designed to power modern games and apps https://github.com/Allan-Nava/nakama-flutter
 Overmind # A character in the game StarCraft

.github/.cspell/words_dictionary.txt

@@ -14,7 +14,6 @@ platformer
 positionable
 postmultiply
 preorder
-prerender
 prerendered
 pressable
 presubmit

README.md

@@ -95,8 +95,6 @@ a Flame game.
 - [flame_lottie][flame_lottie] - Support for [Lottie][lottie] animation in Flame.
 - [flame_network_assets][flame_network_assets] - Helpers to load game assets from
 network.
-- [flame_oxygen][flame_oxygen] for [Oxygen][oxygen]: A lightweight Entity Component System (ECS)
-framework.
 - [flame_rive][flame_rive] for [Rive][rive]: Create interactive animations.
 - [flame_svg][flame_svg] for [flutter_svg][flutter_svg]: Draw SVG files in Flutter.
 - [flame_texturepacker][flame_texturepacker]: Load and use sprite sheets generated with [TexturePacker][texturepacker]
@@ -191,8 +189,6 @@ via an issue, GitHub discussion, or reach out to the team either using the
 [flame_lottie]: https://github.com/flame-engine/flame/tree/main/packages/flame_lottie
 [lottie]: https://airbnb.design/lottie/
 [flame_network_assets]: https://github.com/flame-engine/flame/tree/main/packages/flame_network_assets
-[flame_oxygen]: https://github.com/flame-engine/flame/tree/main/packages/flame_oxygen
-[oxygen]: https://github.com/flame-engine/oxygen
 [flame_rive]: https://github.com/flame-engine/flame/tree/main/packages/flame_rive
 [rive]: https://rive.app/
 [flame_svg]: https://github.com/flame-engine/flame/tree/main/packages/flame_svg

doc/bridge_packages/bridge_packages.md

@@ -56,11 +56,6 @@ Use Lottie animations in Flame (bridge package for [Lottie]).
 Fetch assets over the network.
 :::
 
-:::{package} flame_oxygen
-
-Replace FCS with the Oxygen Entity Component System.
-:::
-
 :::{package} flame_rive
 
 Create interactive animations (bridge package for [Rive]).
@@ -129,7 +124,6 @@ flame_gamepads              <flame_gamepads/flame_gamepads.md>
 flame_isolate               <flame_isolate/flame_isolate.md>
 flame_lottie                <flame_lottie/flame_lottie.md>
 flame_network_assets        <flame_network_assets/flame_network_assets.md>
-flame_oxygen                <flame_oxygen/flame_oxygen.md>
 flame_rive                  <flame_rive/flame_rive.md>
 flame_riverpod              <flame_riverpod/flame_riverpod.md>
 flame_splash_screen         <flame_splash_screen/flame_splash_screen.md>

doc/bridge_packages/flame_oxygen/flame_oxygen.md

@@ -23,7 +23,6 @@
  
     %% Nodes  %%
     
-    A(OxygenGame)
     B(Game):::yellow
     C(FlameGame)
     D(Component)
@@ -32,7 +31,6 @@
 
     %% Flow  %%
 
-    A-- Extends -->B
     F-- Wants -->B
 
     C-- Extends -->D

doc/flame/diagrams/low_level_game_api.md

@@ -8,9 +8,8 @@ and the dialogue runtime; use bridge package `flame_jenny` in order to add it in
 
 :::{package} oxygen
 
-Oxygen is a lightweight Entity Component System framework written in Dart, with a focus on
-performance and ease of use. This package replaces the Flame Component System with the Oxygen
-Entity Component System.
+Oxygen is deprecated and no longer maintained, and we do not recommend using it. The Flame
+Component System is as efficient in almost all cases.
 :::