feat: add strings.repeat builtin #133

Job	Run time
Analyze (go)	4m 51s
Analyze (python)	1m 15s
Analyze (c-cpp)	12m 36s
Analyze (csharp)	4m 57s
Analyze (rust)	7m 41s
Analyze (java-kotlin)	3m 41s
Analyze (javascript-typescript)	4m 22s
	39m 23s

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