introduce DependencyNode mutex

[steiler]

This should fix the issue reported in #1496

[codecov]

Codecov Report

Merging #1505 (d0a887f) into main (4cade7f) will decrease coverage by 0.01%.
Report is 5 commits behind head on main.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##             main    #1505      +/-   ##
==========================================
- Coverage   21.05%   21.04%   -0.01%     
==========================================
  Files          65       65              
  Lines        7073     7075       +2     
==========================================
  Hits         1489     1489              
- Misses       5453     5455       +2     
  Partials      131      131              

Files Changed	Coverage Δ
clab/dependency_manager/dependency_manager.go	24.57% <33.33%> (-0.29%)	⬇️