fix(eslint-plugin): [explicit-module-boundary-types] cyclical reference infinite recursion crash

[tadhgmister]

Fixes #2309

the recursive logic added by #2135 is setup to check members that are not directly exported but used by public members of an exported class, for example here A.method needs to be explicit return type because A ends up being exported:

class A {
    method(){}
}
export class B{
    public ref = A;
}

However when the class refers to itself (or any reference loop) this would cause infinite recursion.

To get around this I've just added a set of all nodes we've already visited so recursion will be bounded.

NOTE: it is very possible the checkedFunctions and alreadyVisited sets can be merged. I tried the unit tests where checkFunctions was removed entirely and isExportedHigherOrderFunction used the alreadyVisited set instead, all unit tests passed but it feels unsound since some nodes like the private fields of a class end up added to the visited set so there may be an edge case where, if isExportedHigherOrderFunction used any visited node to detect it's exported, we'd end up with a false positive for requiring annotations. So to be on the safe side I just added a second set.

[typescript-eslint]

Thanks for the PR, @tadhgmister!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[codecov]

Codecov Report

Merging #2482 into master will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2482      +/-   ##
==========================================
+ Coverage   92.82%   92.84%   +0.02%     
==========================================
  Files         289      289              
  Lines        9294     9296       +2     
  Branches     2600     2600              
==========================================
+ Hits         8627     8631       +4     
+ Misses        321      320       -1     
+ Partials      346      345       -1     

Flag	Coverage Δ
#unittest	92.84% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...plugin/src/rules/explicit-module-boundary-types.ts	89.26% <100.00%> (+1.50%)	⬆️

[bradzacher]

ezpz. LGTM - thanks for this.