Remove `gensym` usage for better precompilation caching

[ChrisRackauckas]

• Catalyst.jl/src/reactionsystem.jl

  Line 548 in 5460da1

  osys = ODESystem(eqs, iv; name = gensym())

• Catalyst.jl/src/dsl.jl

  Line 110 in 5460da1

  return make_rs_expr(:(gensym(:ReactionSystem)), expr)

These should just be hashes instead.

[isaacsas]

@ChrisRackauckas not sure what you are suggesting by using hashes. Can you point me to an example?

[ChrisRackauckas]

using Symbolics
@variables x y
hash(x+y)

So osys = ODESystem(eqs, iv; name = hash(eqs)) , make_rs_expr(:($(hash(expr))), expr) would make it so you have the same equation every time, which means if you make a reaction system with the same equations (and same names of variables) then you'd get exactly the same function and be able to reuse the precompiled cache.

It might only work with precompilation with v1.11 because of JuliaLang/julia#52119, I'm not sure about some of the edges here, but at least it is something the compiler relies on.

[isaacsas]

OK, this sounds like something to look at for Catalyst 16 once MTK 10 is released.