code stype about pass parameter by value, by reference and by rvalue reference

[wadeliuyi]

I see that in function define:
MetaClient::alterEdgeSchema(GraphSpaceID spaceId,
std::string name,
std::vector < cpp2::AlterSchemaItem > items,
nebula::cpp2::SchemaProp schemaProp)

the vector is pass by value,

and when call the function in void HBaseStore::asyncMultiPut(GraphSpaceID spaceId,
PartitionID partId,
std::vector keyValues,
KVCallback cb) {
std::vector<std::pair<std::string, std::vector>> dataList;
// push some value to dataList

ResultCode code = client_->multiPut(tableName, dataList); // pass by value directly.

...
}

and in Metaclient unit test, it pass by value too.

maybe there other place is not right too.

what more: I think pass by rvalue reference is better than pass by value, it can less one rvalue constructor called.

[darionyaphet]

It's like what I talk to @wadeliuyi offline. It's a good suggestion thanks :)