Rework permission checks #1180

Job	Run time
Rustfmt	7s
Build docs	1m 29s
Clippy	48s
Test (MSRV)	1m 19s
Test (stable)	2m 3s
Test (beta)	2m 13s
Test (nightly)	1m 49s
Test (macOS)	1m 29s
Test (Windows)	5m 23s
Test (no features)	1m 7s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 13s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 24s
	20m 24s

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