TypeDB Client Rust dependencies: async runtimes, tokio-stream (#423)

## What is the goal of this PR?

We add dependencies used by TypeDB Client Rust for async runtime
independence tests.

## What are the changes implemented in this PR?

* `tokio-stream`: utility, maps tokio mpsc channel receivers to streams;
* `http`: remove a layer of indirection;
* `smol` and `async-std`: popular async runtimes.

Author: dmitrii-ubskii

.gitignore

@@ -11,3 +11,4 @@ target
 Cargo.lock
 Cargo.toml
 !library/crates/Cargo.toml
+!library/crates/Cargo.lock