Dynamic automatic thread loading
**Describe the bug**
Is there a way to activate/deactivate threads automatically while mining?  Also there seems to be a thread affinity issue when SMT is enabled for Zen 1/1.5 Threadripper/EPYC.  Disabling SMT with memory interleave set to "channel" provides full performance while using stock thread affinity settings for XMRIG with SMT enabled and memory channel set to "auto" or other than "channel" (which should result in only 16 threads used) results in reduced hash rates.  Setting memory interleave to channel forces NUMA mode.

**To Reproduce**
Run XMRIG with thread balancing

**Expected behavior**
Run full threads during operations which use 1MB L3 per thread or less on CPU's which do not have 2MB of L3 per thread. (Ryzen 1/1.5), Intel.  Also upcoming algorithms may need dynamic loading as they may require more than 2MB of L3 per thread which would make thread dynamic loading on current CPU's good to have.

**Required data**
 - OS: ALL

**Additional context**
Some algorithms/coins such as GR/RTM would gain performance with the ability to load more threads dynamically.
