ast: Cache hashes for containers.
ast: Cache hashes for containers.

This slightly increases the amount of memory allocated (but not the
number of allocs), but it reduces the CPU load by avoiding unnecessary
term hashing in the evaluation.

Signed-off-by: Teemu Koponen <514c492c49408016e397a2f741baa6dd9cf7f3be@styra.com>

tsandall/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,open-policy-agent/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,open-policy-agent/opa,tsandall/opa