[TTFX] Use Packages Extensions to drop Zygote and others when not used.

[lrnv]

TaylorDiff is depending on a lot of stuff it should not, which tanks my TTFX.

As already noted in https://github.com/JuliaDiff/TaylorDiff.jl/issues/52#issuecomment-1707801903_ , It would be very beneficial to leverage package preferences to avoid, say, having Zygote and ReverseDiff as dependencies. Formally, the composability with the AD systems is not a core functionality of the package and could be loaded ONLY when those AD systems are loaded.