Add Getters for IBANValidator's RegexValidator its patterns

[arnaudfnr]

Hi,

For a project I need to have access to the regex used to validate IBANs, therefore I added a couple of getters to make it possible.

@sebbASF I saw that you have been contributing quite a lot recently, have you planned to perform a release ? If yes, do you have an estimation of its date please ? It would be nice if these changes could be added :pray:

[sebbASF]

Note that the validator field is package-protected so you could get access from the relevant package (as is done by the test class). Obviously that is not suitable for a project that is publicly available.