Expose the argument `cancelOther` of `AiSequence::stack` to Lua

By default, all AI packages have mShouldCancelPreviousAi = true. This is problematic, as it makes it difficult to preserve long-running AI packages, such as Follow. There are other AI package options, we should consider exposing them too. Although in this case simply expecting the caller to remove all existing packages with filterPackages is also an option.