Consolidated packm_blk_var2 and var3.

Details:
- Consolidated the functionality previously supported by packm_blk_var2()
  and packm_blk_var3() into a new variant, packm_blk_var1().
- Updates to packm_gen_cxk(), packm_herm_cxk.c(), and packm_tri_cxk()
  to accommodate above changes.
- Removed packm_blk_var3() and retired packm_blk_var2() to
  frame/1m/packm/old.
- Updated all level-3 _cntl_init() functions so that the new, more
  versatile packm_blk_var1 is used for all level-3 matrix packing.