## Objective
Fixes#19884.
## Solution
- Add an internal entity command `insert_with`, which takes a function
returning a component and checks if the component would actually be
inserted before invoking the function.
- Add the same check to `insert_from_world`, since it's a similar
situation.
- Update the `or_insert_with`, `or_try_insert_with`, and `or_default`
methods on `EntityEntryCommands` to use the new command.
Since the function/closure returning the component now needs to be sent
into the command (rather than being invoked before the command is
created), the function now has `Send + 'static` bounds. Pretty typical
for command stuff, but I don't know how/if it'll affect existing users.
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Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
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