Make KeysCollection.Contains methods public.

[eiriktsarpalis]

Fix #75936.

No testing added on the assumption that functional testing on the interface implementation is sufficient. Please let me know if separate testing for the newly exposed APIs is required.

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Issue Details

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Fix #75936.

No testing adding on the assumption that functional testing on the interface implementation is sufficient. Please let me know if separate testing for the newly exposed APIs is required.

Author:	eiriktsarpalis
Assignees:	-
Labels:	area-System.Collections, new-api-needs-documentation
Milestone:	-

[campersau]

Should the commit message / title be Make KeysCollection.Contains methods public. instead of ContainsKey?

[eiriktsarpalis]

It should -- I've updated the PR title so that it shows up correctly in the final commit. Thanks.