Built-in commands should return Results whenever possible

[alice-i-cecile]

First: I'll note that most of the built in commands as phrased in #17043 do not (yet) return errors, and I think updating everything is out of scope for this PR.

That being said, multiple paths have been laid for built-in commands to return handled errors.

The first path: all built-in commands are now exported as functions in the command and entity_command modules. If any of them were rephrased to return an error, then this would immediately be possible:

entity.queue_fallible(insert(Team::Blue).handle_error_with(warn()));

The more common case of using the built-in shorthand functions would use the default global error handler, which defaults to panicking but can be configured:

entity.insert(Team::Blue);

Originally posted by @cart in #17215 (comment)

[alice-i-cecile]

Not happening in time, but still high value to do. Bumping milestones.

[JaySpruce]

I've been aware of this issue since it was opened, but I was never really sure what to do about it, because from what I could tell it was basically already solved: most commands that could return Result did. For example, insert doesn't have any failure modes beyond the entity not existing, which already returns a Result.

You mentioned in the linked PR (#20303) that, rather than creating the Result within the command, the corresponding World method should return one, which I think is the crux of the issue.

If the World methods return Result, so will the commands using them. That turns this into more of a "Bevy needs to use Result more" problem, which I think has a separate issue open.