Various fixes for OE (#418)

* Add default for getting chunk allocator state

Makes the API same between the two configurations.

* Reduce address space usage for Open Enclave

* Fix OE Pal concept

* Add support for Pal not to provide time.

The lazy return of pages to the OS uses a simple time
based heuristic.  This enables a PAL to not support time,
and return the memory to a central pool immediately.

* Update src/backend/backend.h

Co-authored-by: Amaury Chamayou <amaury@xargs.fr>

Co-authored-by: Amaury Chamayou <amaury@xargs.fr>

src/pal/pal_open_enclave.h

@@ -19,6 +19,8 @@ namespace snmalloc
       UNUSED(str);
       oe_abort();
     }
+    static constexpr size_t address_bits = Aal::address_bits;
+    static constexpr size_t page_size = Aal::smallest_page_size;
   };
 
   using OpenEnclaveBasePAL = PALNoAlloc<OpenEnclaveErrorHandler>;