Retired portions of bli_kernel_3m/4m_macro_defs.h.

Details:
- Removed sections of bli_kernel_[4m|3m]_macro_defs.h that defined
  4m/3m-specific blocksizes after realizing that this can be done in
  bli_gemm[4m|3m]_cntl.c, since that is (mostly) the only place they
  are used.
- The maximum cache values for 4m/3m are stll needed when computing mem
  pool dimensions in bli_mem_pool_macro_defs.h. As a workaround, "local"
  definitions in terms of the regular cache blocksizes are now in place.
- Similarly, the register blocksizes for 4m/3m are still needed in
  bli_kernel_post_macro_defs.h. As a workaround, "local" definitions in
  terms of the regular register blocksizes are now in place.