Add anoma-bytearray-{to, from}-anoma-contents builtins

[paulcadman]

The anoma-bytearray-{to, from}-anoma-contents are intended to be used to convert to/from atoms representing ByteArrays. These builtins are required temporarily until Anoma Node makes ByteArray representation uniform across all of its APIs.

We represent ByteArrays in nock as a cell:

[size contents]

Where size is the size of the ByteArray and contents is an Atom representing the bytes in LSB ordering.

The size is required in general because the encoding of ByteArrays to Atoms is ambiguous. For example the ByteArrays [0x01; 0x00] and [0x01] are represented by 1.

Some Anoma ByteArrays like keys and signatures are represented using on the contents atom because the size is constant.

Users of Anoma APIs have to strip / add size information from ByteArrays depending on where the data is used. The new builtins provide this facility.

These builtins are temporary because it's been agreed with Anoma engineering team to change the Anoma APIs to make the ByteArray representation uniform, i.e always represent ByteArrays using [size content]. When this is implemented in Anoma Node we can remove these builtins.

builtin anoma-bytearray-to-anoma-contents
axiom toAnomaContents : ByteArray -> Nat;

builtin anoma-bytearray-from-anoma-contents
axiom fromAnomaContents :
  -- | The size of the ByteArray
  Nat
  -- | The contents of the ByteArray
  -> Nat
  -- | The resulting ByteArray
  -> ByteArray;