storcon: make pageserver AZ id mandatory (#8856)

## Problem
https://github.com/neondatabase/neon/pull/8852 introduced a new nullable
column for the `nodes` table: `availability_zone_id`

## Summary of changes
* Make neon local and the test suite always provide an az id
* Make the az id field in the ps registration request mandatory
* Migrate the column to non-nullable and adjust in memory state
accordingly
* Remove the code that was used to populate the az id for pre-existing
nodes

storage_controller/src/persistence.rs

@@ -105,7 +105,6 @@ pub(crate) enum DatabaseOperation {
     ListMetadataHealthOutdated,
     GetLeader,
     UpdateLeader,
-    SetNodeAzId,
 }
 
 #[must_use]
@@ -325,31 +324,6 @@ impl Persistence {
         }
     }
 
-    pub(crate) async fn set_node_availability_zone_id(
-        &self,
-        input_node_id: NodeId,
-        input_az_id: String,
-    ) -> DatabaseResult<()> {
-        use crate::schema::nodes::dsl::*;
-        let updated = self
-            .with_measured_conn(DatabaseOperation::SetNodeAzId, move |conn| {
-                let updated = diesel::update(nodes)
-                    .filter(node_id.eq(input_node_id.0 as i64))
-                    .set((availability_zone_id.eq(input_az_id.clone()),))
-                    .execute(conn)?;
-                Ok(updated)
-            })
-            .await?;
-
-        if updated != 1 {
-            Err(DatabaseError::Logical(format!(
-                "Node {node_id:?} not found for setting az id",
-            )))
-        } else {
-            Ok(())
-        }
-    }
-
     /// At startup, load the high level state for shards, such as their config + policy.  This will
     /// be enriched at runtime with state discovered on pageservers.
     pub(crate) async fn list_tenant_shards(&self) -> DatabaseResult<Vec<TenantShardPersistence>> {
@@ -1110,7 +1084,7 @@ pub(crate) struct NodePersistence {
     pub(crate) listen_http_port: i32,
     pub(crate) listen_pg_addr: String,
     pub(crate) listen_pg_port: i32,
-    pub(crate) availability_zone_id: Option<String>,
+    pub(crate) availability_zone_id: String,
 }
 
 /// Tenant metadata health status that are stored durably.