refactor(parser): make `Source::set_position` safe #6485

Job	Run time
Doc	50s
Check and Build (windows-latest)	2m 22s
Cargo Deny	16s
Check and Build (ubuntu-latest)	1m 5s
Check and Build (macos-14)	40s
Format	14s
Clippy	1m 18s
Test (windows-latest)	2m 31s
Spell Check	5s
Check Unused Dependencies	7s
Test (ubuntu-latest)	1m 32s
Test (macos-14)	58s
Check Wasm	1m 28s
Conformance	2m 43s
	16m 9s

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