Use macros in nested functions

Created by: simonbyrne

I would like to be able to call macros (e.g. @localmem) from functions which are called (perhaps indirectly) from the @kernel function. e.g. here: https://github.com/CliMA/ClimaCore.jl/blob/14712189be7c4a2ea8bc329955b219c17c604ca3/src/Operators/spectralelement.jl#L564-L565

I guess we could do this by explicitly passing the secret __ctx__ arg through, but it's not clear that is part of the API.