Test integration of PartitionAlloc/HardenedPartitionAlloc in Tor Browser

PartitionAlloc/HardenedPartitionAlloc (https://github.com/struct/HardenedPartitionAlloc) have some interesting security properties we like to use (see: legacy/trac#20998 (moved) for a similar ticket wrt jemalloc). We should try to test them and compare them to jemalloc with partitioning enabled.

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