Create labdir next to clab file

[hellt]

no one will miss the old behavior of creating the labdir in the $pwd

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.95%. Comparing base (bf7e377) to head (a1cf01d).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2394      +/-   ##
==========================================
+ Coverage   51.88%   51.95%   +0.06%     
==========================================
  Files         172      172              
  Lines       17302    17300       -2     
==========================================
+ Hits         8978     8988      +10     
+ Misses       7381     7373       -8     
+ Partials      943      939       -4     

Files with missing lines	Coverage Δ
clab/config.go	67.69% <100.00%> (ø)
types/topo_paths.go	74.13% <100.00%> (+2.10%)	⬆️

... and 3 files with indirect coverage changes