Finder: selectors filters can't be extended

[ClotildeToullec]

When searching for examples in the finder, a list of methods are called on the receiver to compare with the expected result.
This list is built from a green list, and a black list is rejected. See #allSelectorsToTestInMethodFinder.

This issue is: both green list (approvedSelectorsForMethodFinder) and black list (#forbiddenSelectorsForMethodFinder) are hard-coded and can't be extended.

This has been an issue in Moose, where we have custom methods in Collection. These methods have behavior that should not be triggered by the Finder, but we can't add them to the black list without intervening in Pharo code. Linked to moosetechnology/MooseIDE#1298