Allow destructuring in command parameters #897

Job	Run time
Build docs	2m 14s
Clippy	1m 42s
Test (MSRV)	4m 44s
Test (stable)	3m 47s
Rustfmt	11s
Test (beta)	4m 21s
Test (nightly)	2m 6s
Test (macOS)	3m 32s
Test (Windows)	8m 35s
Test (no features)	1m 54s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	3m 1s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 15s
	37m 22s

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