Bevy 0.12

[NiseVoid]

Includes some work to put svg behind a feature flag, which reduces deps for people who don't use it, and makes migrating easier while bevy_svg hasn't been migrated yet.

Big issues for this migration would be:

• The asset migration, especially changes to asset loaders, asset events, and load_internal changing to a new embedded asset approach
• Rendering changes, especially those introduced by Reorder render sets, refactor bevy_sprite to take advantage bevyengine/bevy#9236