Flatten return type of symbolization #701

Job	Run time
Benchmark	7m 24s
Generate documentation	20s
Check generated C header	48s
Build [ubuntu-latest, 1.63.0, dev, ]	3m 13s
Lint with clippy	53s
Build [ubuntu-latest, 1.63.0, release, ]	3m 31s
Check code formatting	16s
No-op rebuilds	50s
Build [ubuntu-latest, stable, dev, ]	33s
Build [ubuntu-latest, stable, release, ]	40s
Test with release build	2m 48s
Build [macos-latest, 1.63.0, dev, ]	4m 17s
Test and coverage	2m 41s
Test with address sanitizer	3m 53s
Build [macos-latest, 1.63.0, release, ]	4m 25s
Test with leak sanitizer	3m 5s
Build [macos-latest, stable, dev, ]	47s
Build [macos-latest, stable, release, ]	1m 1s
Build [ubuntu-latest, stable, dev, --no-default-features]	35s
	42m 0s

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