fix: add KeyGet for built_in_functions

[cs1137195420]

part of: #209 add KeyGet(), KeyGet2() and KeyGet3() for built_in_functions

[casbin-bot]

@EmperorYP7 @sheny1xuan please review

[hsluoyz]

@cs1137195420 plz also port all related tests from Go to CPP

[hsluoyz]

@JalinWang plz review

[JalinWang]

There are too many if-else statements, making the code hard to understand. Would it be better if you add some comments to illustrate what the case the code is dealing with?

[cs1137195420]

@hsluoyz @JalinWang I tested the functions in built_in_functions with Casbin's test cases, and found that some of the original keymatch functions still failed in some examples. I will implement these error functions with regular matching later, and upload them together with the test case. For example, KeyMatch3 will return false for the regular expression /proxy/{id}/*/{res} and the string /proxy/myid/res/res2/res3.

[hsluoyz]

@cs1137195420 a good practice is using exactly the same logic as Golang, just port Go code to C++.

[cs1137195420]

@cs1137195420 a good practice is using exactly the same logic as Golang, just port Go code to C++.

I agree with you. That is exactly what I am going to do next.

[hsluoyz]

@cs1137195420 fix all errors:

[hsluoyz]

@JalinWang @sheny1xuan @EmperorYP7 plz review

[hsluoyz]

@sheny1xuan

[hsluoyz]

@cs1137195420 fix:

[github-actions[bot]]

:tada: This PR is included in version 1.50.4 :tada:

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