feat: add Avoid unnecessary setState

[incendial]

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix
[X] New rule
[ ] Changes an existing rule
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

Closes #332

[codecov]

Codecov Report

Merging #346 (e484bbd) into master (316f32c) will increase coverage by 0.40%.
The diff coverage is 97.14%.

@@            Coverage Diff             @@
##           master     #346      +/-   ##
==========================================
+ Coverage   77.70%   78.10%   +0.40%     
==========================================
  Files         143      145       +2     
  Lines        3315     3385      +70     
==========================================
+ Hits         2576     2644      +68     
- Misses        739      741       +2     

Impacted Files	Coverage Δ
...c/analyzers/lint_analyzer/rules/rules_factory.dart	90.47% <0.00%> (-4.53%)	⬇️
...necessary_setstate/avoid_unnecessary_setstate.dart	100.00% <100.00%> (ø)
...rules_list/avoid_unnecessary_setstate/visitor.dart	100.00% <100.00%> (ø)

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