Make cmd_depth task-local

[thestr4ng3r]

Racy otherwise (depths from different tasks will "add up")

[codecov-io]

Codecov Report

Merging #14888 into master will decrease coverage by <.01%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master   #14888      +/-   ##
==========================================
- Coverage   38.32%   38.32%   -0.01%     
==========================================
  Files         960      960              
  Lines      314069   314070       +1     
==========================================
- Hits       120376   120375       -1     
- Misses     193693   193695       +2

Impacted Files	Coverage Δ
libr/core/cconfig.c	88.79% <100%> (ø)	⬆️
libr/core/core.c	44.56% <100%> (-0.03%)	⬇️
libr/core/task.c	56.97% <100%> (+0.12%)	⬆️
libr/cons/cons.c	52.88% <100%> (+0.05%)	⬆️
libr/core/cmd.c	45.99% <80%> (ø)	⬆️
libr/core/project.c	57.47% <0%> (-0.34%)	⬇️
libr/core/visual.c	13.11% <0%> (ø)	⬆️

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