feat: switch to `tracing` (#223) #918

Job	Run time
Rustfmt	13s
Test (MSRV)	5m 22s
Build docs	2m 26s
Clippy	51s
Test (stable)	2m 4s
Test (beta)	2m 0s
Test (nightly)	2m 4s
Test (macOS)	3m 22s
Test (Windows)	3m 48s
Test (no features)	1m 16s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 21s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 22s
	26m 9s

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