Add apply function for tuple

[adayton1]

No description provided.

[trws]

This looks good, but how does it differ from invoke? Actually glancing at it, the existing invoke may be missing a forward where one would be appropriate, but perhaps that should be rectified and apply be an alias to invoke?

[adayton1]

I guess it is the same thing as camp::invoke. Initially I was looking for a camp equivalent to std::apply (https://en.cppreference.com/w/cpp/utility/apply) since std::invoke and std::invoke_r take a parameter pack instead of a tuple. I could certainly make camp::apply an alias to camp::invoke and add the appropriate forwarding in camp::invoke.

[adayton1]

@trws, I made apply an alias to invoke and added forwarding to invoke_with_order. Let me know what you think.

[trws]

Sounds good to me. I think when we re-work the API for RAJA and CAMP on the way to 1.0 this is something to fix too, make apply the one for this and use invoke for its now established purpose.