CONTRACTS: check function for loop normal form

[remi-delmas-3000]

Co-authored with @qinheping

Will be used to check that loops have a form that allows to apply function contract instrumentation.

Extracted from #7541, can only be tested once all features are in place.

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[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (f6f7057) 78.51% compared to head (c575fbf) 78.51%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7627   +/-   ##
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  Coverage    78.51%   78.51%           
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  Files         1674     1674           
  Lines       191935   191935           
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  Hits        150704   150704           
  Misses       41231    41231           

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[feliperodri]

@tautschnig @peterschrammel if you have the time, could you review this PR?