Refactor duplicate code in `type_coercion/functions.rs` #4900

Job	Run time
linux build test	4m 4s
Run sqllogictests with the sqlite test suite	1h 15m 28s
cargo test hash collisions (amd64)	8m 59s
cargo test 'extended_tests' (amd64)	38m 27s
	2h 6m 58s

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