Deprecate DeferredWorld::query by generalizing QueryState::query_mut

[chescock]

Objective

Make the API for querying using QueryState more consistent.

Currently, the way to get a Query from a QueryState and World is the QueryState::query and QueryState::query_mut methods, but the way to get a Query from QueryState and DeferredWorld is the DeferredWorld::query method.

This is also surprising because DeferredWorld derefs to World, and there is a World::query method that creates a QueryState instead of creating a Query.

Solution

Generalize QueryState::query_mut to take impl Into<DeferredWorld<'w'>>. Add a missing From impl so that this actually works with &mut DeferredWorld, and add DeferredWorld::to_unsafe_world_cell to recover the full 'w lifetime in the implementation.

Deprecate DeferredWorld::query in favor of QueryState::query_mut.