Thread-safe reproject with ThreadFunctors

[rafaqz]

Havent run this yet, but should be close to working.

@asinghvi17 turns out it needs 2 layers of functors to deal with is3d

Discussed in #287

Changelog:

• Refactor the apply pipeline to get rid of closures in favour of Applicators, which are able to run apply on arrays, geoms and featurecollections.
• Add a TaskFunctors struct that allows one to use individual functors per task. This allows thread safety for reentrant C APIs.
• Refactor reproject, in the Proj backend, to use this functionality

[asinghvi17]

Lol - I had a very similar approach, including an equivalent of the ApplyToN wrapper, but using TaskLocalValues.jl. But if we never reuse the value in a task then we don't need that package.

My struct was a bit different:

struct KnownInputDimTransformation{Z, M, T}
    transf::T
end

function KnownInputDimTransformation{Z, M}(transf::T) where {Z, M, T}
    KnownInputDimTransformation{Z, M, T}(transf)
end

function (t::KnownInputDimTransformation{Z, M, T})(p) where {Z, M, T}
    if Z
        return t.transf(GI.x(p), GI.y(p), GI.z(p))
    else
        return t.transf(GI.x(p), GI.y(p))
    end
end

currently does not handle Z and M but could be trivially extended to handle those and add default values if we want.

[asinghvi17]

Boom

julia> @be GO.reproject($mpolys, $trans)
Benchmark: 13 samples with 1 evaluation
 min    7.543 ms (75012 allocs: 3.300 MiB)
 median 7.617 ms (75012 allocs: 3.300 MiB)
 mean   7.975 ms (75012 allocs: 3.300 MiB, 2.72% gc time)
 max    11.873 ms (75012 allocs: 3.300 MiB, 35.34% gc time)

julia> @be GO.reproject($mpolys, $trans; threaded = true)
Benchmark: 45 samples with 1 evaluation
 min    1.934 ms (75275 allocs: 3.496 MiB)
 median 1.970 ms (75275 allocs: 3.496 MiB)
 mean   2.229 ms (75275 allocs: 3.496 MiB, 5.59% gc time)
 max    6.006 ms (75275 allocs: 3.496 MiB, 65.74% gc time)