Adding mapdl.solution() to enter in solution processor

[germa89]

This allows us to do:

# define model
mapdl.solution()
mapdl.solve()

Which is more natural than using mapdl.slashsolution

[codecov]

Codecov Report

Merging #2293 (a11cbf6) into main (e3885fb) will increase coverage by 1.20%.
Report is 117 commits behind head on main.
The diff coverage is 91.42%.

@@            Coverage Diff             @@
##             main    #2293      +/-   ##
==========================================
+ Coverage   86.39%   87.59%   +1.20%     
==========================================
  Files          45       45              
  Lines        7977     8435     +458     
==========================================
+ Hits         6892     7389     +497     
+ Misses       1085     1046      -39     

[clatapie]

LGTM!