FindElement

[cicr99]

Searches for a specific key within an array and returns its index, asserting the validity of the index and size constraints.

Reference : https://github.com/starkware-libs/cairo-lang/blob/efa9648f57568aad8f8a13fbf027d2de7c63c2c0/src/starkware/cairo/common/find_element.cairo#L29

Depends on #245 for accessing global variables.