Add check for usage of Rat.SetString in math/big with an overflow error

[hackallcode]

Rat.SetString in math/big in Go before 1.16.14 and 1.17.x before 1.17.7
has an overflow that can lead to Uncontrolled Memory Consumption.

It is the CVE-2022-23772.

Fix of #810

[ccojocar]

It looks good, please could you use the helper function instead to check the call as mentioned in the comment. Thanks

[codecov-commenter]

Codecov Report

Merging #819 (847b188) into master (fb587c1) will decrease coverage by 0.01%.
The diff coverage is 73.17%.

@@            Coverage Diff             @@
##           master     #819      +/-   ##
==========================================
- Coverage   74.37%   74.35%   -0.02%     
==========================================
  Files          49       50       +1     
  Lines        3091     3124      +33     
==========================================
+ Hits         2299     2323      +24     
- Misses        727      735       +8     
- Partials       65       66       +1     

Impacted Files	Coverage Δ
helpers.go	43.14% <0.00%> (-0.89%)	⬇️
call_list.go	92.59% <80.00%> (+0.43%)	⬆️
rules/math_big_rat.go	86.95% <86.95%> (ø)
issue.go	76.92% <100.00%> (ø)
rules/rulelist.go	100.00% <100.00%> (ø)

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