Improve token semantics #1002

Job	Run time
Test (macOS)	1m 56s
Test (nightly)	1m 43s
Test (stable)	2m 25s
Test (beta)	2m 41s
Build docs	42s
Examples	43s
Test (Windows)	4m 42s
Check minimal versions	57s
Test (native-tls)	2m 24s
MSRV	0s
Test (no default features)	55s
Test (no cache)	2m 16s
Test (no gateway)	1m 51s
Test (unstable Discord API features)	2m 24s
Test (chrono, chrono)	54s
Test (unstable API + typesize, default unstable typesize, true)	48s
Test (builder without model, builder, true)	47s
Test (unstable Discord API (no default features), unstable, true)	17s
	28m 25s

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