ChainRulesCore projection & ReverseDiff.TrackedArray

When using ReverseDiff over Zygote, its tracked arrays will often be turned into arrays of TrackedReal:

julia> using ReverseDiff, Zygote

julia> _, back = pullback(x -> cumsum(x .^ 3), rand(3))
([0.0417770851525806, 0.08898338554941161, 0.13448629430576223], Zygote.var"#52#53"{typeof(∂(#11))}(∂(#11)))

julia> ta = ReverseDiff.track([1,2,3.0]);

julia> back(ta)[1]
3-element Vector{ReverseDiff.TrackedReal{Float64, Float64, Nothing}}:
 TrackedReal<Ha5>(2.1671946936904316, 0.0, BcR, ---)
 TrackedReal<J2r>(1.9592562290038964, 0.0, BcR, ---)
 TrackedReal<5TB>(1.147101768209455, 0.0, BcR, ---)

The cause of this is that ChainRulesCore's projection mechanism looks at the eltype, and decides that it needs correcting:

julia> using ChainRulesCore

julia> pt = ProjectTo(ta)
ProjectTo{AbstractArray}(element = ProjectTo{Real}(), axes = (Base.OneTo(3),))

julia> pt(ta)  # this works fine, TrackedArray
3-element ReverseDiff.TrackedArray{Float64, Float64, 1, Vector{Float64}, Vector{Float64}}:
 TrackedReal<EIm>(1.0, 0.0, BcR, 1, 96O)
 TrackedReal<I8K>(2.0, 0.0, BcR, 2, 96O)
 TrackedReal<9lo>(3.0, 0.0, BcR, 3, 96O)

julia> pr = ProjectTo(rand(3))
ProjectTo{AbstractArray}(element = ProjectTo{Float64}(), axes = (Base.OneTo(3),))

julia> pr(ta)  # makes a Vector{TrackedReal}
3-element Vector{ReverseDiff.TrackedReal{Float64, Float64, ReverseDiff.TrackedArray{Float64, Float64, 1, Vector{Float64}, Vector{Float64}}}}:
 TrackedReal<KBA>(1.0, 0.0, BcR, 1, 96O)
 TrackedReal<29L>(2.0, 0.0, BcR, 2, 96O)
 TrackedReal<7oX>(3.0, 0.0, BcR, 3, 96O)

julia> map(pr.element, ta)  # this is what projection calls, as TrackedReal <: Float64 is false
3-element Vector{ReverseDiff.TrackedReal{Float64, Float64, ReverseDiff.TrackedArray{Float64, Float64, 1, Vector{Float64}, Vector{Float64}}}}:
 TrackedReal<AQQ>(1.0, 0.0, BcR, 1, 96O)
 TrackedReal<5IS>(2.0, 0.0, BcR, 2, 96O)
 TrackedReal<2yC>(3.0, 0.0, BcR, 3, 96O)

I think this should probably be avoided, by adding methods to (::ProjectTo)(::TrackedArray) which bypass this behaviour. Since ReverseDiff already depends on CRC, no extra deps are required.

Start by reading ChainRulesCore's ProjectTo dispatch and ReverseDiff.TrackedArray definitions, then reproduce the shown ProjectTo(ta) and ProjectTo(rand(3))(ta) behavior. Done means projecting a TrackedArray preserves its tracked-array form instead of producing an array of TrackedReal, while ordinary array projection continues to work.