Allow casting between bytea and integer types.

Allow casting between bytea and integer types.

This allows smallint, integer, and bigint values to be cast to and
from bytea. The bytea value is the two's complement representation of
the integer, with the most significant byte first. For example:

  1234::bytea -> \x000004d2
  (-1234)::bytea -> \xfffffb2e

Author: Aleksander Alekseev <[email protected]>
Reviewed-by: Joel Jacobson <[email protected]>
Reviewed-by: Yugo Nagata <[email protected]>
Reviewed-by: Peter Eisentraut <[email protected]>
Reviewed-by: Michael Paquier <[email protected]>
Reviewed-by: Dean Rasheed <[email protected]>
Discussion: https://postgr.es/m/CAJ7c6TPtOp6%2BkFX5QX3fH1SVr7v65uHr-7yEJ%3DGMGQi5uhGtcA%40mail.gmail.com