Add test for file offset calculation #433

Job	Run time
Test and coverage	1m 39s
Test with release build	2m 25s
Build [ubuntu-latest, 1.65.0, dev, --workspace]	5m 35s
No-op rebuilds	32s
Build [ubuntu-latest, 1.65.0, release, --workspace]	6m 40s
Build [ubuntu-latest, stable, dev, --workspace]	26s
Test with address sanitizer	3m 38s
Benchmark	7m 57s
Build [ubuntu-latest, stable, release, --workspace]	34s
Test with leak sanitizer	1m 28s
Generate documentation	21s
Build [macos-latest, 1.65.0, dev, --workspace]	8m 15s
Check generated C header	40s
Build [macos-latest, 1.65.0, release, --workspace]	9m 13s
Lint with clippy	39s
Build [macos-latest, stable, dev, --workspace]	37s
Check code formatting	13s
Build [macos-latest, stable, release, --workspace]	1m 6s
Build [ubuntu-latest, stable, dev, --no-default-features]	31s
	52m 29s

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