Rework permission checks #1144

Job	Run time
Clippy	50s
Rustfmt	12s
Test (MSRV)	1m 15s
Build docs	1m 22s
Test (stable)	2m 6s
Test (beta)	2m 2s
Test (nightly)	1m 56s
Test (macOS)	1m 49s
Test (Windows)	3m 53s
Test (no features)	1m 12s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 15s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 23s
	19m 15s

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