refact(GenerateDAG): general

[antoinegelloz]

• rename some variables
• make methods private when it makes sense
• add context files to image instead of node
• tests to internal

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 58.96%. Comparing base (da3b77a) to head (e88f69b).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/dib/generate_dag.go	87.50%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #615      +/-   ##
==========================================
+ Coverage   58.94%   58.96%   +0.01%     
==========================================
  Files          51       51              
  Lines        2353     2349       -4     
==========================================
- Hits         1387     1385       -2     
+ Misses        860      858       -2     
  Partials      106      106              

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[gminh474]

LGTM