`#[moxie::query]` attribute macro

[anp]

Need to be able to mark parameters as #[slot] (part of the slot tuple generated).

Caching should be opt-in (out?). If cached, arguments should be assumed to be part of the input unless marked #[volatile] and output should be assumed Clone.

Need to handle local vs Send queries.

Should allow getting things from the illicit environment and treating them as inputs.

Should also generate doc comments explaining which parameters have which behavior w.r.t caching.