pageserver: move page_service's import basebackup / import wal to mgmt API (#8292)

I want to fix bugs in `page_service`
([issue](https://github.com/neondatabase/neon/issues/7427)) and the
`import basebackup` / `import wal` stand in the way / make the
refactoring more complicated.

We don't use these methods anyway in practice, but, there have been some
objections to removing the functionality completely.

So, this PR preserves the existing functionality but moves it into the
HTTP management API.

Note that I don't try to fix existing bugs in the code, specifically not
fixing
* it only ever worked correctly for unsharded tenants
* it doesn't clean up on error

All errors are mapped to `ApiError::InternalServerError`.

storage_controller/src/node.rs

@@ -226,7 +226,7 @@ impl Node {
         fn is_fatal(e: &mgmt_api::Error) -> bool {
             use mgmt_api::Error::*;
             match e {
-                ReceiveBody(_) | ReceiveErrorBody(_) => false,
+                SendRequest(_) | ReceiveBody(_) | ReceiveErrorBody(_) => false,
                 ApiError(StatusCode::SERVICE_UNAVAILABLE, _)
                 | ApiError(StatusCode::GATEWAY_TIMEOUT, _)
                 | ApiError(StatusCode::REQUEST_TIMEOUT, _) => false,

storage_controller/src/service.rs

@@ -151,6 +151,10 @@ struct ServiceState {
 /// controller API.
 fn passthrough_api_error(node: &Node, e: mgmt_api::Error) -> ApiError {
     match e {
+        mgmt_api::Error::SendRequest(e) => {
+            // Presume errors sending requests are connectivity/availability issues
+            ApiError::ResourceUnavailable(format!("{node} error sending request: {e}").into())
+        }
         mgmt_api::Error::ReceiveErrorBody(str) => {
             // Presume errors receiving body are connectivity/availability issues
             ApiError::ResourceUnavailable(