malloc: index heaps using heap ID rather than NUMA node

malloc: index heaps using heap ID rather than NUMA node

Switch over all parts of EAL to use heap ID instead of NUMA node
ID to identify heaps. Heap ID for DPDK-internal heaps is NUMA
node's index within the detected NUMA node list. Heap ID for
external heaps will be order of their creation.

This breaks the ABI, so document the changes.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>