rust: simply use TryInto to convert slice to array
Since our rust module depends on TryInto, there's no point to avoid using it.
While rewriting copy_into_array(), I noticed CPython interface doesn't check
the length of the p1/p2 values, which is marked as TODO.
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}