feat: instrumented joinsets and other custom spawns

[noxware]

Current solution

Exposes a handle.spawn_with(fut, |f: TracedFuture| { ... }) to allow spawning instrumented/traced futures through custom spawn APIs (like JoinSet::spawn).

Example

let handle = TelemetryHandle::current();
let mut set: JoinSet<()> = JoinSet::new();
handle.spawn_with(fut, |f| set.spawn(f));

For reviewers

Most important changes are at recorder/mod.rs and traced.rs.

Other

Closes #301

[noxware]

Added some comments to help with the code review :)

[noxware]

This is the new API, the root part of the PR.

[noxware]

This is what used to be Traced (kinda).

[noxware]

This is the concreate type of the spawn_with closure. It composes WakeTracked and TaskDumped (if enabled), without dynamic dispatching.

Note: It can also be called Traced<F> as the name is now free. Although we also have other explicit "traced" types like TracedRuntime. Opinons?

[noxware]

An explicit name is needed to pattern match the enum.

[noxware]

Empty is just used to transit the state safely.

[noxware]

This file contains the auxiliar changes to make spawn_with work by exposing the TracedFuture type. It has the most important changes.

[noxware]

We rely on pin projection to avoid writting unsafe code.

[yulnr]

Looks good to me! happy we could keep the instrumented flag an internal concern.
Leaving some minor comments

[noxware]

@yulnr It should be done now :)

[rcoh]

Nice!