It's informal, but I wouldn't call it slang. It means I have the qualities, characteristics, and/or talents, abilities, etc. to do the job. You often use it with "to....". "I have what it takes to complete the job." "I have what it takes to be the best firefighter in the world." "He has what it takes to win the marathon."

Dark Panther has what it takes

i have what it takes = i am qualified = i am capable of 不是俚语而是习惯用语

superman has what it takes to turn the world upside down.