Poor performance of `LinearMap`

And maybe List, Array,... too. I have not looked into the code yet. But, from what I see on Task Manager, I guess it's because calling realloc too often.

[IsaacShelton]

Yes, LinearMap really really sucks. It's not meant to be efficient, just simple and predictable.

It's a temporary stopgap that must to be replaced with a proper HashMap type before v2.8 is released.

It's been so long and we don't even have a proper standard HashMap type yet, just temporary LinearMap introduced in early versions of v2.8