refactor[venom]: move dfs order to CFGAnalysis

[charles-cooper]

What I did

move dfs order calculation from domtree to cfg analysis.

remove unnecessary calculation of domtree in sccp

How I did it

How to verify it

Commit message

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Description for the changelog

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[codecov]

Codecov Report

Attention: Patch coverage is 41.17647% with 20 lines in your changes missing coverage. Please review.

Project coverage is 44.83%. Comparing base (658f0c4) to head (24f90a6).

Files with missing lines	Patch %	Lines
vyper/venom/analysis/cfg.py	30.43%	16 Missing ⚠️
vyper/venom/analysis/dominators.py	66.66%	3 Missing ⚠️
vyper/venom/passes/sccp/sccp.py	50.00%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (658f0c4) and HEAD (24f90a6). Click for more details.

HEAD has 137 uploads less than BASE

Flag	BASE (658f0c4)	HEAD (24f90a6)
	139	2

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4330       +/-   ##
===========================================
- Coverage   91.34%   44.83%   -46.51%     
===========================================
  Files         112      112               
  Lines       15921    15935       +14     
  Branches     2691     2693        +2     
===========================================
- Hits        14543     7145     -7398     
- Misses        943     8182     +7239     
- Partials      435      608      +173     

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