add finalizers with command and error ref

[kevingentile]

This is an attempt to resolve #1893. This logic mirrors the existing OnFinalize pattern but passes along a reference to *Command and error.

Usage:

cobra.OnFinalizeCmd(func(cmd *cobra.Command, err error) {
    if errors.Is(err, FooErr) {
        // [...]
    }
    value := cmd.Context().Value(key{})
    // [...]
})