Compiler allows reusing of the same argument name when defining a function

[matteojug]

When defining a function, the compiler allows reusing the same name for different args, while interpreting the clarity code raises an error.

Failing test:

#[test]
fn reuse_arg_name() {
    crosscheck_compare_only("(define-private (foo (a int) (a int)) a) (foo 1 2)")
}

results in:

assertion `left == right` failed: Compiled and interpreted results diverge! (define-private (foo (a int) (a int)) a) (foo 1 2)
compiled: Ok(Some(Int(2)))
interpreted: Err(Unchecked(NameAlreadyUsed("a")))
  left: Ok(Some(Int(2)))
 right: Err(Unchecked(NameAlreadyUsed("a")))

[obycode]

Adding a note here that the interpreter catches this at runtime, not at deploy time, so for example if you just have:

(define-public (foo (a int) (a int)) (ok a))

This will deploy fine, but only when you call it will it report a runtime error:

error: Runtime Error: Runtime error while interpreting ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.contract-3: Unchecked(NameAlreadyUsed("a"))

[matteojug]

Done in #510