refactor: Use const ref in DecimalUtil #15004

Job	Run time
Build	49m 19s
Build with Clang	0s
Spark Aggregate Fuzzer	15m 42s
Presto Fuzzer	15m 45s
Presto Bias Fuzzer	0s
Spark Fuzzer	15m 46s
Aggregation Fuzzer with Presto as source of truth	16m 17s
Join Fuzzer	17m 28s
RowNumber Fuzzer	15m 36s
Window Fuzzer with Presto as source of truth	17m 33s
Exchange Fuzzer	16m 5s
Spark Bias Fuzzer	0s
Signature Changes	4s
Biased Aggregation Fuzzer with Presto as source of truth	0s
Writer Fuzzer with Presto as source of truth	17m 24s
Biased Expression Fuzzer with Only Added/Updated Functions and Presto as source of truth	0s
	3h 16m 59s

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