Add on systat -vm the ability to display the physical and kernel memory percent usage.

[araujo]

Summary

Original PR: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=203917

Original output:
   14 users    Load  0.31  0.31  0.27

Mem:KB    REAL            VIRTUAL            
        Tot   Share      Tot    Share    Free
Act  113596   17720   703456    25104 1672360
All  239340   20096  1371300    36548

PR output:
   14 users    Load  0.31  0.31  0.27

Phy: 35%     REAL       VIRTUAL     Kmem: 17%
Mem:    Tot   Share      Tot    Share    Free
Act  503616   16696  1370680    27544 1307516
All  554684   18308  1967904    45132

Remake the patch:
   13 users    Load  0.52  0.32  0.27
   Mem usage:  69%Phy 26%Kmem
Mem: KB    REAL            VIRTUAL
                    Tot   Share      Tot    Share    Free
Act 2681368   62976  9332364   113272 2413564  count
All 2709644   71600  9422012   175616          pages

Personally, I pretty much like have the percentage of MEM there.
Note that I have added an additional space between Mem: and KB.

Test Plan

systat -vm on different terminals and console.

[araujo]

Remove an extra "Mem:" that is not necessary and was in the original PR patch.

[bapt]

usr.bin/systat/vmstat.c

316

Adding a space before Phy and Kmem would be imho a good idea for readability

[araujo]

usr.bin/systat/vmstat.c

316

I agree, however it uses the same approach as used on Proc:
Example:
0.4%Sys, 0.0%Intr....

So, to make it consistent, I did in that way.