Upgrade to Bevy v0.12

[thombruce]

At the time of writing, Bevy 0.12 is almost done (https://github.com/bevyengine/bevy/milestone/14) and I have to assume a release is just around the corner.

Migration guide: https://bevyengine.org/learn/migration-guides/0.11-0.12/

Let's not be too hasty though; we still have other dependencies which need to be updated to support Bevy 0.12:

• [x] Bevy: https://bevyengine.org/news/bevy-0-12/
• [x] bevy-inspector-egui: https://github.com/jakobhellermann/bevy-inspector-egui/pull/157
• [x] bevy_common_assets: https://github.com/NiklasEi/bevy_common_assets/pull/21
• [x] bevy_spatial: https://github.com/laundmo/bevy-spatial/commit/60cdda7a825703df30c9bf7dd0e532befa6fb022
• [x] leafwing-input-manager: https://github.com/Leafwing-Studios/leafwing-input-manager/pull/408
• [x] bevy_fluent: https://github.com/kgv/bevy_fluent/pull/35 (see comment on issue)
• [x] bevy_rapier2d: https://github.com/dimforge/bevy_rapier/pull/439
• [x] bevy_asset_loader: https://github.com/NiklasEi/bevy_asset_loader/pull/158
• [x] bevy-ui-navigation: https://github.com/nicopap/ui-navigation/pull/39
• [x] bevy_tiling_background (currently using a fork: https://github.com/rparrett/bevy_tiling_background, "tex-typo" branch)

Also note the window icon special case (https://github.com/bevyengine/bevy/issues/1031) and update winit to an appropriate version if the version used by Bevy also moves. This appears not to have cahanged.

[thombruce]

Just look at those links I was able to add!! Five out of the eight crates I need to update are already on top of this. Fantastic stuff!

[thombruce]

Bevy Fluent API is expected to change before a new release. See comment: https://github.com/kgv/bevy_fluent/pull/35#issuecomment-1796105319

kgv points to PR https://github.com/kgv/bevy_fluent/pull/36 available as a "quick upgrade to Bevy 0.12", so that's a check for bevy_fluent. 👍

6 down, 4 to go.