Avoid copies in getChecked (cherry-pick from upstream) (#151)

[AlexandruLorinti]

Summary

Duplicate of PR merged on npu/release/19.x #151
Cherry-pick from upstream llvm llvm/llvm-project#147721; adding std::move to getChecked method.

JIRA ticket

• E-105998

Related PR in NPU Compiler and/or OpenVINO repository with sub-module update

• PR-xxx

Other related tickets

List tickets for additional work, eg, something was found during review but you agreed to address it in another Jira

• E-xxxxx

[AlexandruLorinti]

Updated expected copy count from "1" to "2" for CopyCountGet and CopyCountGetChecked tests, as there are currently 2 copies generated, while in previous npu-plugin-llvm there was just 1 copy generated.

In current npu-plugin-llvm as well as in upstream llvm there are 2 copies as the test calls first verifyInvariants which internally calls verify, in mlir/include/mlir/IR/StorageUniquerSupport.h:201

if (failed(ConcreteT::verifyInvariants(emitErrorFn, args...)))