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>

crates/server/src/error.rs

@@ -176,12 +176,6 @@ pub enum ConfigError {
     HttpPort,
     #[error("rpki: no caches are listed")]
     RpkiNoCaches,
-    #[error("policy: give the script's path or its source, and not both")]
-    PolicySource,
-    #[error("policy: cannot read {path}: {error}")]
-    PolicyFile { path: String, error: String },
-    #[error("policy: {0}")]
-    Policy(#[from] bgp_policy::PolicyError),
     #[error("rpki: the port of cache {0:?} is required")]
     RpkiCachePort(String),
     #[error("peer {peer:?}: {problem}")]
@@ -198,10 +192,6 @@ pub enum ConfigError {
 pub enum PeerProblem {
     #[error("endpoint is missing")]
     MissingEndpoint,
-    #[error("{0}")]
-    Policy(#[from] bgp_policy::PolicyError),
-    #[error("names the policy function {0:?}, and there is no policy script")]
-    NoPolicyScript(String),
     #[error("endpoint is invalid: {0}")]
     Endpoint(Box<ConfigError>),
     #[error("remote_asn must be non-zero")]