[Enhancement](column) remove ColumnString terminating zero and add a data_version for pblock (#12456)

1. remove ColumnString terminating zero
    2. add a data_version for pblock
    3. change EncryptionMode to enum class

be/src/runtime/fold_constant_executor.cpp

@@ -179,7 +179,6 @@ Status FoldConstantExecutor::_init(const TQueryGlobals& query_globals) {
 
     _runtime_profile = _runtime_state->runtime_profile();
     _runtime_profile->set_name("FoldConstantExpr");
-    SCOPED_ATTACH_TASK(_runtime_state.get());
     _mem_tracker = std::make_unique<MemTracker>("FoldConstantExpr");
     _mem_pool.reset(new MemPool(_mem_tracker.get()));