feat: add strings.repeat builtin #135

Job	Run time
Analyze (python)	1m 18s
Analyze (go)	4m 56s
Analyze (csharp)	4m 54s
Analyze (java-kotlin)	3m 34s
Analyze (rust)	7m 51s
Analyze (c-cpp)	12m 33s
Analyze (javascript-typescript)	4m 30s
	39m 36s

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