Generates an implementation of the Plugin::queries() trait function using
all previously-expanded #[query] attribute macros. Due to Rust’s macro
expansion ordering, all #[query] functions must come before this macro
to ensure they are seen and added.
An attribute on a function that creates an associated struct that implements
the Hipcheck Rust SDK’s Query trait. The function must have the signature
fn(&mut PluginEngine, content: impl serde::Deserialize) -> hipcheck_sdk::Result<impl serde::Serialize>. The generated struct’s name is
the pascal-case version of the function name (e.g. do_something() ->
DoSomething).