Async trait methods for no_std

Features like async-trait, avoid using Box and dyn.

This crate is ready for #![no_std] when PR68524 merged.

Features

• [X] basic function async fn for trait.
• [ ] support default Implementations.
• [ ] test more feature support.

Usage

```rust use asynctraitstatic::async_trait;

async fn hello() -> u8 { 1 }

[async_trait]

trait AsyncFnTrait { async fn run(&self); }

struct AsyncStruct;

[async_trait]

impl AsyncFnTrait for AsyncStruct { async fn run(&self) { hello().await; } }

```