BRP methods naming pass

[Leinnan]

Consider renaming the methods to be a little more hierarchical.
It would make sense to group them more, something like:
bevy/mutate_component -> bevy/world/components/mutate
bevy/list_resources -> bevy/world/resources/list
bevy/insert_resource -> bevy/world/resources/insert
bevy/remove_resource -> bevy/world/resources/remove
bevy/mutate_resource -> bevy/world/resources/mutate

[mweatherley]

For a little bit of context, the reason that I didn't find the time to implement this in my PR is basically that I got stunlocked thinking about how to namespace existing things 😅

For example:

• Does bevy/get belong in some component namespace?
• What about bevy/query? (By contrast, something like bevy/list is a more clear-cut "yes" to me.)
• Should there be something like an entity namespace? Entities and components are often interconnected, and query is just as much about locating entities as it is about finding component values.

[Leinnan]

I was thinking a bit about this and I would split all of the existing calls into bevy/world and bevy/registry. Then in bevy/world we could have categories for resources and components and what does not fit there could be in bevy/world.

[Leinnan]

@mweatherley do you feel that you would want to do it and make a PR for it before 0.16? Because on the one hand I don't know if I have enough time for it right know myself, but I would really want to make that change before BRP gets more popular and changing it would mean that more people need to adapt to breaking change.

[mweatherley]

@Leinnan I don't think I will realistically get around to changing this before 0.16 myself.