Fix: OptimizeIndex concurrent conflict detection causes UnrecoverableError

[zpf121]

Close #3328

Description

When multiple optimize index operations occur (either from timer or manual trigger), the system throws UnrecoverableError("There should be no concurrent optimize txns") incorrectly.

Message

[02:07:36.025] [1667169] [critical] Error: Aborted
   6# infinity::UnrecoverableError at /infinity/src/common/utility/exception_impl.cpp:84
  11# infinity::NewTxn::CheckConflictTxnStore at /infinity/src/storage/new_txn/new_txn_impl.cpp:3953
  12# infinity::NewTxn::CheckConflictTxnStores at /infinity/src/storage/new_txn/new_txn_impl.cpp:4558
  13# infinity::NewTxnManager::CheckConflict1 at /infinity/src/storage/new_txn/new_txn_manager_impl.cpp:228
  14# infinity::NewTxn::Commit at /infinity/src/storage/new_txn/new_txn_impl.cpp:2082
  15# infinity::NewTxnManager::CommitTxn at /infinity/src/storage/new_txn/new_txn_manager_impl.cpp:317
  16# infinity::OptimizationProcessor::NewNotifyOptimize at /infinity/src/storage/bg_task/optimization_process_impl.cpp:99
  17# infinity::OptimizationProcessor::Process at /infinity/src/storage/bg_task/optimization_process_impl.cpp:181

Reproduce

slow test：reldeb_restart_test