Auto merge of #3732 - JoJoDeveloping:tree-borrows-protector-end-write, r=RalfJung

TB: Refine protector end semantics

Tree Borrows has protector end tag semantics, namely that protectors ending cause a [special implicit read](https://perso.crans.org/vanille/treebor/diff.0.html) on all locations protected by that protector that have actually been accessed. See also #3067.

While this is enough for ensuring protectors allow adding/reordering reads, it does not prove that one can reorder writes. For this, we need to make this stronger, by making this implicit read be a write in cases when there was a write to the location protected by that protector, i.e. if the permission is `Active`.

There is a test that shows why this behavior is necessary, see `tests/fail/tree_borrows/protector-write-lazy.rs`.

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