Moves intern and label modules into bevy_ecs

[mnmaita]

Objective

• Attempts to solve two items from Remove or shrink bevy_utils #11478.

Solution

• Moved intern module from bevy_utils into bevy_ecs crate and updated all relevant imports.
• Moved label module from bevy_utils into bevy_ecs crate and updated all relevant imports.

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Migration Guide

• Replace bevy_utils::define_label imports with bevy_ecs::define_label imports.
• Replace bevy_utils::label::DynEq imports with bevy_ecs::label::DynEq imports.
• Replace bevy_utils::label::DynHash imports with bevy_ecs::label::DynHash imports.
• Replace bevy_utils::intern::Interned imports with bevy_ecs::intern::Interned imports.
• Replace bevy_utils::intern::Internable imports with bevy_ecs::intern::Internable imports.
• Replace bevy_utils::intern::Interner imports with bevy_ecs::intern::Interner imports.

[james7132]

Mind fixing CI? The lints seem like they should be fixable by using cast::<()> instead of as.

[mnmaita]

Mind fixing CI? The lints seem like they should be fixable by using cast::<()> instead of as.

Done, rebased and updated the migration guide. Feel free to take a second look at it now @james7132. Thanks!

[mnmaita]

@james7132 I did a change that fixed the issue with Interned in the docs, but now there's a different one... Could you please help me figure out why Schedule is giving errors during doc generation? I don't really know what's the cause of this issue. Thanks!

[james7132]

I think you just need to make this [`Schedule`](crate::schedule::Schedule).

[mnmaita]

This should be fixed in the latest change @james7132

[mnmaita]

@james7132 something failed during the merge queuing process (and I see no logs on the step that failed... Maybe it was just a blip in the matrix during artifact upload?). I've updated the branch, if you could queue this one again I'll appreciate it.