Add RULE from break to breakOn

[Bodigrim]

bytestring has rewrite rules like

{-# RULES
"ByteString specialise takeWhile (x /=)" forall x.
    takeWhile (x `neWord8`) = fst . breakByte x
"ByteString specialise takeWhile (/= x)" forall x.
    takeWhile (`neWord8` x) = fst . breakByte x
  #-}

{-# RULES
"ByteString specialise dropWhile (x /=)" forall x.
    dropWhile (x `neWord8`) = snd . breakByte x
"ByteString specialise dropWhile (/= x)" forall x.
    dropWhile (`neWord8` x) = snd . breakByte x
  #-}

{-# RULES
"ByteString specialise break (x ==)" forall x.
    break (x `eqWord8`) = breakByte x
"ByteString specialise break (== x)" forall x.
    break (`eqWord8` x) = breakByte x
  #-}

I think we should do the same, rewriting Data.Text.break as Data.Text.breakOn and same for lazy text.

(See https://discourse.haskell.org/t/blog-5x-speedup-changing-break-to-elemindex/13946 for context)