Chained `EntityCommands` create useless temporary archetypes

## What problem does this solve or what need does it fill?

When calling `EntityCommands::insert` (or `remove`, or the bundle equivalents) repeatedly within a single system, all intermediate archetypes are constructed.

Suppose we have an entity with the component `A`, and call `.insert(B)` and `.insert(C)`. Despite only caring about enities that have the component sets (archetypes) `{A}` and `{A, B, C}`, the archetype `{A, B}` is also constructed.

This has both immediate performance costs, and reduces general program performance as these empty archetypes continue to exist.

## What solution would you like?

Automatically batch all component-modifying methods on `EntityCommands` into a single `modify_bundle` `EntityCommand` for each entity before processing them.

## What alternative(s) have you considered?

Users can acheive this effect by manually grouping these calls, but this is limited to pure insertion or pure removal `EntityCommands`, non-obvious and can lead to less clear code.

We could do even smarter batching strategies, e.g generating `spawn_batch` calls, but that is a) much harder and b) less immediately important.

## Additional context

This is essential to ensuring that #1481 is both usable and maintains correctness at all times, otherwise these temporary archetypes are constructed and can fail the assertions generated.