bpo-40915: Fix mmap resize bugs on Windows (GH-29213)

bpo-40915: Fix mmap resize bugs on Windows (GH-29213)

(original patch by eryksun)

Correctly hand various failure modes when resizing an mmap on Windows:

* Resizing a pagefile-backed mmap now creates a new mmap and copies data
* Attempting to resize when another mapping is held on the same file raises an OSError
* Attempting to resize a nametagged mmap raises an OSError if another mapping is held with the same nametag