Remove policy scripts

Rhai made a decision about a route cost one to three microseconds,
some two hundred times what the same costs in Rust. That was bearable
where a function is asked once for an UPDATE, and is not where every
route is weighed against every peer, as it is when routes are passed
on. What is wanted of a policy (mark routes by where they came from,
mark what is announced, let communities say who is told what) needs no
language; it is to be configuration, done natively.

Kept from that work: route selection goes by a LOCAL_PREF that policy
set on a route from an external peer, and the lab's configuration can
be added to by a phase.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -69,7 +69,7 @@ jobs:
         env:
           RUSTFLAGS: ""
         run: |
-          for target in message message_body attrs policy prefix_text config rtr netlink; do
+          for target in message message_body attrs prefix_text config rtr netlink; do
             mkdir -p "corpus/$target"
             cargo fuzz run "$target" "corpus/$target" "seeds/$target" -- -max_total_time=60
           done