Feature suggestion: query async* and composite query async*

[vporton]

Please, let introduce query async* and composite query async* functions (without the right to modify actor-level variables or call non-query functions) that would be callable from query and composite query. composite query async* functions should have the right to call query and composite query functions.

composite query func f(): async* {
  await x.g(); // g is a query function
};

Without this feature, need to write a query/composite query function as a "monolith", without splitting it into async* functions, what is both inconvenient and likely produces longer WASM code.