Incorrect Comparison in Vyper

Summary

### Impact bytestrings can have dirty bytes in them, resulting in the word-for-word comparison to give incorrect results, e.g. ```vyper b1: Bytes[32] = b"abcdef" b1 = slice(b1, 0, 1) b2: Bytes[32] = b"abcdef" t: bool = b1 == b2 # incorrectly evaluates to True ``` even without dirty nonzero bytes, because there is no comparison of the length, two bytestrings can compare to equal if one ends with `"\x00"`. ```vyper b1: Bytes[32] = b"abc\0" b2: Bytes[32] = b"abc" t: bool = b1 == b2 # incorrectly evaluates to True ``` ### Patches fixed in https://github.com/vyperlang/vyper/commit/2c73f8352635c0a433423a5b94740de1a118e508