Attribute Macro topo::nested

#[nested]

Transforms a function declaration into a topologically-nested function invoked with macro syntax to attach its call tree's (sub)topology to the parent topology.

A macro transformation is used to capture unique callsite information from the invoking function. In the current implementation, we synthesize a unique std::any::TypeId at each callsite which can be used to identify the chain of topological invocations.