[command] Reorder Scheduler operations (#4261)

Fixes several cases where calling scheduler operations from a command callback could result in NPEs or other issues.

Co-authored-by: Tyler Veness <calcmogul@gmail.com>

wpilibNewCommands/src/main/native/include/frc2/command/CommandScheduler.h

@@ -367,5 +367,8 @@ class CommandScheduler final : public nt::NTSendable,
   frc::Watchdog m_watchdog;
 
   friend class CommandTestBase;
+
+  template <typename T>
+  friend class CommandTestBaseWithParam;
 };
 }  // namespace frc2