Introduce force flag for new deletion API (#12588)

## Problem

The force deletion API should behave like the graceful deletion API - it
needs to support cancellation, persistence, and be non-blocking.

## Summary of Changes

- Added a `force` flag to the `NodeStartDelete` command.
- Passed the `force` flag through the `start_node_delete` handler in the
storage controller.
- Handled the `force` flag in the `delete_node` function.
- Set the tombstone after removing the node from memory.
- Minor cleanup, like adding a `get_error_on_cancel` closure.

---------

Co-authored-by: Aleksandr Sarantsev <aleksandr.sarantsev@databricks.com>

control_plane/storcon_cli/src/main.rs

@@ -76,6 +76,12 @@ enum Command {
     NodeStartDelete {
         #[arg(long)]
         node_id: NodeId,
+        /// When `force` is true, skip waiting for shards to prewarm during migration.
+        /// This can significantly speed up node deletion since prewarming all shards
+        /// can take considerable time, but may result in slower initial access to
+        /// migrated shards until they warm up naturally.
+        #[arg(long)]
+        force: bool,
     },
     /// Cancel deletion of the specified pageserver and wait for `timeout`
     /// for the operation to be canceled. May be retried.
@@ -952,13 +958,14 @@ async fn main() -> anyhow::Result<()> {
                 .dispatch::<(), ()>(Method::DELETE, format!("control/v1/node/{node_id}"), None)
                 .await?;
         }
-        Command::NodeStartDelete { node_id } => {
+        Command::NodeStartDelete { node_id, force } => {
+            let query = if force {
+                format!("control/v1/node/{node_id}/delete?force=true")
+            } else {
+                format!("control/v1/node/{node_id}/delete")
+            };
             storcon_client
-                .dispatch::<(), ()>(
-                    Method::PUT,
-                    format!("control/v1/node/{node_id}/delete"),
-                    None,
-                )
+                .dispatch::<(), ()>(Method::PUT, query, None)
                 .await?;
             println!("Delete started for {node_id}");
         }