Substitute pow2bin allocator with a dlmalloc based allocator (#71)

* Add dlmalloc_strat allocator strategy
 - Use mspace variant to ease encapsulation
 - Make pow2bins and dlmalloc cmake selectable
* Add unit tester for dlmalloc, rework single_heap, pow2bins unit testers
accordingly
 - add dlmalloc get_used/get_avail, and have all strats allocators also have a get_used
 - Rework memallocator unit tests: bin size is per strat, alignment is verified in singleheap
* bugfix: dlmalloc exposed that the pingpong test would write past end of
allocation with -w 32
* iostream leakage/mixed usage of cerr and fprintf(stderr

---------

Signed-off-by: Aurelien Bouteiller <aurelien.bouteiller@amd.com>

[ROCm/rocshmem commit: b835de6cd5]

projects/rocshmem/scripts/functional_tests/driver.sh

@@ -429,6 +429,10 @@ TestOther() {
   ExecTest  "pingpong"         2       8            1
   ExecTest  "pingpong"         2       32           1
 
+  ExecTest  "pingall"          2       1            1
+  ExecTest  "pingall"          2       8            1
+  ExecTest  "pingall"          2       32           1
+
   # This test requires more contexts than workgroups
   export ROCSHMEM_MAX_NUM_CONTEXTS=1024
   ExecTest  "teamctxinfra"     2       1            1