Un-support force_trivial parameter for LocalVector. Instead, users should use resize_uninitialized.

[Ivorforce]

• Follow-up of Core: Add resize_initialized and resize_uninitialized to Vector and LocalVector #104522

The parameter force_trivial was always just a way to resize the LocalVector without calling default initializers (to save time).
Now, this is no longer required - users can simply call resize_uninitialized! This makes it explicit where a resize is happening without filling values.

This PR should not change behavior, just simplify matters and improve code style.

Notes

• I've checked changed_items and _cull_hits, they never called resize so the force_trivial parameter was useless for both.
• force_trivial behavior handling is bubbled up to PooledList. It is somewhat questionable whether it is appropriate here, because it is only used to create one object at a time. Still, this is outside the scope of this PR to change.
• _active_map and freelist use a trivial type so they don't initialize on resize (regardless of force_trivial). I took the opportunity to make this explicit using resize_uninitialized, as we'll make that a goal soon anyway.

[lawnjelly]

Oof yeah, not being able to remove force_trivial easily is a pain for backward compatibility with third party stuff.

[Ivorforce]

Since we may want to remove the tight parameter too in favour of something like reserve_exact, we may have the opportunity to remove both at once :)

[lawnjelly]

Yeah, I've never thought the tight parameter was a good idea, and suggested reserving to exact size myself around that time it was added.

[lawnjelly]

Assuming passes CI...

[Repiteo]

Thanks!