Refine ambiguous labels "PROCESSORS" and "THREADS" in screen output

[xinchenhou]

In ABACUS's screen output, the labels PROCESSORS and THREADS are ambiguous and cannot clearly reflect the actual parallel configuration.

For instance, I executed the task with 28 MPI processes and 1 OpenMP thread per process using the command:
mpirun -np 28 ./abacus

However, the output shows misleading information as below:

 ---------------------------------------------------------
 Self-consistent calculations for electrons
 ---------------------------------------------------------
 SPIN    KPOINTS         PROCESSORS  THREADS     
 1       1               28          28          
 ---------------------------------------------------------

Existing problems

1. The term PROCESSORS is not precise. It refers to MPI tasks in practice, rather than physical CPU processors. Using PROCESSES or MPI PROCS would be more appropriate.
2. The term THREADS is confusing. It displays the total threads instead of threads per MPI rank, which may cause misunderstanding of the running setup.

[QuantumMisaka]

@xinchenhou Thanks for your issue ! I'm the develop of THREADS layer, and I make THREADS to that based on :
1.THREADS can be both TOTAL THREADS or THREADS per RANK, but use THREADS per RANK will be too long in the output layer.
2. PROCESSORS is refer to as the total process launched by MPI, so THREADS refer to as the total threads used is better for consistent. make THREADS as threads per rank will also lead to confusing while processors present total rank.

（用中文说的话两个词代表的就是“进程数”和“线程数”的概念）

However, I‘m also consider that RANKS may be better than PROCESSORS. I do think this problem need more discussion