[Fusion] Added pre-merge validation rule "RootMutationUsedRule"

[glen-84]

Summary of the changes (Less than 80 chars)

• [Fusion] Added pre-merge validation rule "RootMutationUsedRule".

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.32%. Comparing base (02e8e31) to head (1e5df67).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7865      +/-   ##
==========================================
- Coverage   74.32%   74.32%   -0.01%     
==========================================
  Files        2880     2880              
  Lines      150189   150189              
  Branches    17468    17468              
==========================================
- Hits       111631   111627       -4     
- Misses      32743    32748       +5     
+ Partials     5815     5814       -1     

Flag	Coverage Δ
unittests	74.32% <ø> (-0.01%)	⬇️

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