proxy: Remove the endpoint filter cache (#12488)

## Problem

The endpoint filter cache is still unused because it's not yet reliable
enough to be used. It only consumes a lot of memory.

## Summary of changes

Remove the code. Needs a new design.

neondatabase/cloud#30634

proxy/src/control_plane/errors.rs

@@ -99,10 +99,6 @@ pub(crate) enum GetAuthInfoError {
 
     #[error(transparent)]
     ApiError(ControlPlaneError),
-
-    /// Proxy does not know about the endpoint in advanced
-    #[error("endpoint not found in endpoint cache")]
-    UnknownEndpoint,
 }
 
 // This allows more useful interactions than `#[from]`.
@@ -119,8 +115,6 @@ impl UserFacingError for GetAuthInfoError {
             Self::BadSecret => REQUEST_FAILED.to_owned(),
             // However, API might return a meaningful error.
             Self::ApiError(e) => e.to_string_client(),
-            // pretend like control plane returned an error.
-            Self::UnknownEndpoint => REQUEST_FAILED.to_owned(),
         }
     }
 }
@@ -130,8 +124,6 @@ impl ReportableError for GetAuthInfoError {
         match self {
             Self::BadSecret => crate::error::ErrorKind::ControlPlane,
             Self::ApiError(_) => crate::error::ErrorKind::ControlPlane,
-            // we only apply endpoint filtering if control plane is under high load.
-            Self::UnknownEndpoint => crate::error::ErrorKind::ServiceRateLimit,
         }
     }
 }
@@ -200,9 +192,6 @@ impl CouldRetry for WakeComputeError {
 
 #[derive(Debug, Error)]
 pub enum GetEndpointJwksError {
-    #[error("endpoint not found")]
-    EndpointNotFound,
-
     #[error("failed to build control plane request: {0}")]
     RequestBuild(#[source] reqwest::Error),