feat: no more tuples in Call

[lwshang]

Description

Many Rust Canister developers (including myself) have some complaints about the inter-canister call syntax:

It's quite annoying that the arguments to calls and their results have to be written as singleton tuples in order for ArgumentEncoder and ArgumentDecoder to be derived for types that implement CandidType

The new Call type fixes it!

Say canister "abcde-xxxxx" has following Candid interface:

service : {
    echo : (u32) -> (u32);
}

Before, we have to put both args and returns in singleton tuples:

let res: (u32,) = call("abcde-xxxxx", "echo", (1u32,)).await().unwrap();

Now, we can:

let res: u32 = Call::new("abcde-xxxxx", "echo").with_arg(1u32).call().await.unwrap();

How Has This Been Tested?

e2e-tests/tests/call.rs

Checklist:

• The title of this PR complies with Conventional Commits.
• I have edited the CHANGELOG accordingly.
• I have made corresponding changes to the documentation.