Update `CurrentApplicationInfo` and add support for editing it #5884

Job	Run time
Test (stable)	2m 26s
Test (beta)	2m 26s
Build docs	46s
Test (Windows)	4m 36s
Examples	2m 34s
Test (native-tls)	2m 29s
Test (macOS)	2m 6s
Test (no default features)	50s
Check minimal versions	34s
Test (no cache)	2m 13s
MSRV	0s
Test (nightly)	1m 40s
Test (no gateway)	1m 40s
Test (unstable Discord API features)	2m 48s
Test (zlib compression)	2m 36s
Test (zstd compression)	2m 18s
Test (zlib and zstd compression)	2m 32s
Test (chrono, chrono)	58s
Test (unstable API + typesize, default unstable typesize, true)	52s
Test (builder without model, builder, true)	37s
Test (unstable Discord API (no default features), unstable, true)	30s
	37m 31s

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