fix continuous callbacks

[ChrisRackauckas]

Before, this was:

function continuous_affect!_kernel(affect!,event_idx,u,t,p)
    @loop for i in ((event_idx,); (blockIdx().x-1) * blockDim().x + threadIdx().x)
        @views @inbounds affect!(FakeIntegrator(u[:,i],t,p[:,i]))
        nothing
    end
    nothing
end

@vchuravy could I get a quick check to see if this makes sense? This a kind of weird case where we really just want to launch a kernel mostly to hit the same abstraction: event_idx is even an integer most of the time, but we want to run this function on the GPU just because the values are already on the GPU.

[codecov]

Codecov Report

Merging #70 into master will not change coverage.
The diff coverage is 0.00%.

@@          Coverage Diff           @@
##           master     #70   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files           1       1           
  Lines         264     264           
======================================
  Misses        264     264           

Impacted Files	Coverage Δ
src/DiffEqGPU.jl	0.00% <0.00%> (ø)

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