Performance improvement + C interface + env control

• Significant performance improvement (~2x)
• new C interface for TiMemory
  • requires variable assignment and freeing
    • void* atimer = TIMEMORY_AUTO_TIMER("")
    • FREE_TIMEMORY_AUTO_TIMER(atimer)
• command-line tools: timem (UNIX-only) and pytimem
• Environment control
  • TIMEMORY_VERBOSE
  • TIMEMORY_DISABLE_TIMER_MEMORY
  • TIMEMORY_NUM_THREADS_ENV
  • TIMEMORY_NUM_THREADS
  • TIMEMORY_ENABLE
  • TIMEMORY_TIMING_FORMAT
  • TIMEMORY_TIMING_PRECISION
  • TIMEMORY_TIMING_WIDTH
  • TIMEMORY_TIMING_UNITS
  • TIMEMORY_TIMING_SCIENTIFIC
  • TIMEMORY_MEMORY_FORMAT
  • TIMEMORY_MEMORY_PRECISION
  • TIMEMORY_MEMORY_WIDTH
  • TIMEMORY_MEMORY_UNITS
  • TIMEMORY_MEMORY_SCIENTIFIC
  • TIMEMORY_TIMING_MEMORY_FORMAT
  • TIMEMORY_TIMING_MEMORY_PRECISION
  • TIMEMORY_TIMING_MEMORY_WIDTH
  • TIMEMORY_TIMING_MEMORY_UNITS
  • TIMEMORY_TIMING_MEMORY_SCIENTIFIC
• Ability of push/pop default formatting
• improved thread-local singleton using C++ shared_ptrs
  • automatic merge and deletion of manager instances at sub-thread exit
• Hard-code python exe into timemory python scripts
• Various fixes (plotting, argparse, etc.)
• Minor fix to avoid very rare FPE when serializing
• fix to TiMemoryConfig.cmake when installed via sudo
• self-cost available in manager + plotting safeguards
• Improved singleton deletion
• alternative colors for when len(_types) == 1 in plotting
• plotting label fix