Add blacksmith to polars-feedstock

[pavelzw]

Checklist:

• I want to request (or revoke) access to an opt-in CI resource:
  • Pinged the relevant feedstock team(s)
  • Added a small description explaining why access is needed

polars is OOMing while compiling on windows: conda-forge/polars-feedstock#366

@conda-forge/polars

[jaimergp]

I added namespace too so you can check both providers to see which one works better.