* The AddressSpaceManager now requests address space in specified granule
sizes and registers those allocations with an external ArenaMap.
* The DefaultArenaMap is a (somewhat erroneously named) Pagemap sparse array /
tree for these provenance roots. Nothing is stored on non-StrictProvenance
architectures.
* In the Sandbox test, give an example of a different ArenaMap structure, which
confines amplification to sandbox memory.
* Adjust some other tests to compile.
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