Add context as second parameter for the mutation function

[asermax]

This PR adds a context that's passed as the second parameter to the mutationFn in a mutation. This change allows access to the mutation's meta (similar to query functions), which I find useful for passing in configurations (similarly as the case mentioned in https://github.com/TanStack/query/discussions/7045#discussioncomment-9151048). I've also included the mutationKey in the context, since it came up in a similar discussion #3504.

While this context could eventually include other information, I kept this initial contribution small and simple as to not get all tangled up with all the typing :sweat_smile:

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