deprecated legacy methods async_call and async_call_promise #96

Job	Run time
Contracts (nightly) / Rust tests	2m 47s
Contracts (nightly) / Test Coverage	7m 34s
Contracts (nightly) / Clippy linter check	1m 7s
Contracts (nightly) / Wasm tests	15m 11s
	26m 39s

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