Log Message:
opa: Update to 0.55.0

Changes:
0.55.0
------
This release contains a mix of new features, bugfixes and a new builtin
function.

### Honor `default` keyword on functions

Previously if a function was defined with a `default` value, OPA would
ignore it. Now the `default` function is honored if all functions with
the same name are undefined. For example,

The value of a `default` function follows the same conditions as that
of a `default` rule. In addition, a `default` function satisfies the
following properties:

- same arity as other functions with the same name
- arguments should only be plain variables ie. no composite values
- argument names should not be repeated

### New Built-In Function: crypto.parse_private_keys

`crypto.parse_private_keys` returns zero or more private keys from the
given encoded string containing DER certificate data.  If the input
contains a list of one or more concatenated PEM blocks, then the
built-in will output the parsed private keys represented as objects.