cache factories and use fast pass strings

[stevenbrix]

This PR caches default activation factories and also converts us from using String and allocating HSTRING to just using fast-pass string references to avoid unnecessary string allocations

[jeffdav]

🤷‍♂️

[tristanlabelle]

Nice! Do you see a path to using fast pass strings in normal API calls as well?

[stevenbrix]

Nice! Do you see a path to using fast pass strings in normal API calls as well?

yes, i want to spend a few hours improving the way we make abi calls so that we don't do this anymore:

let abi = wrapper.toAbi { $0 }

and instead do something like

AbiHelper.toAbi(thing1, thing2) { thing1Abi, thing2Abi in 

   doAbiCall(thing1Abi, thing2Abi);
}