FlightSQL example is broken

[viirya]

Describe the bug

FlightSQL example (arrow-flight/examples/flight_sql_server.rs) is broken. Running cargo test -p arrow-flight --features=flight-sql-experimental --examples got compilation error:

error[E0433]: failed to resolve: use of undeclared crate or module `fs`
   --> arrow-flight/examples/flight_sql_server.rs:504:17
    |                                                                                                              
504 |         let _ = fs::remove_file(path.clone());
    |                 ^^ use of undeclared crate or module `fs`  
                                                                                                                                                                                                                                       
error[E0412]: cannot find type `FlightSqlServiceClient` in this scope                                              
   --> arrow-flight/examples/flight_sql_server.rs:490:47                                                           
    |                                                                                                              
490 |     async fn client_with_uds(path: String) -> FlightSqlServiceClient {                                       
    |                                               ^^^^^^^^^^^^^^^^^^^^^^
    |                               
...

To Reproduce

Expected behavior

cargo test -p arrow-flight  --features=flight-sql-experimental --examples

   Compiling arrow-flight v29.0.0 (/arrow-rs/arrow-flight)
    Finished test [unoptimized + debuginfo] target(s) in 1.76s
     Running unittests examples/flight_sql_server.rs (target/debug/examples/flight_sql_server-609b62f910a8643f)

running 1 test
test tests::test_select_1 ... ok

Additional context

[alamb]

label_issue.py automatically added labels {'arrow-flight'} from #3387