Rework permission checks #1146

Job	Run time
Rustfmt	13s
Test (MSRV)	1m 21s
Build docs	1m 27s
Test (stable)	1m 57s
Clippy	57s
Test (beta)	2m 3s
Test (nightly)	1m 39s
Test (macOS)	1m 57s
Test (Windows)	4m 17s
Test (no features)	1m 7s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 20s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 20s
	19m 38s

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