Feature: Wrap GoogleMock (gmock) in ut-core with UT_ mocking macros + examples

[Ulrond]

Problem/Opportunity

ut-core wraps the gtest backend (include/ut_gtest.h, src/cpp_source/ut_gtest.cpp) with UT_ASSERT_* / UT_ADD_TEST macros, but it does not wrap GoogleMock (gmock). There is currently no supported way to author mocks for a C++ interface under test, which is the core need when unit-testing abstract HAL/AIDL C++ interfaces.

The pinned googletest release (1.15.2, fetched by build.sh into framework/gtest/<target>/googletest-1.15.2) is the combined distribution — it already contains googlemock/ alongside googletest/. So gmock source is present; it is simply not built, linked, initialised, or wrapped.

Proposed Solution

Wrap gmock in ut-core, mirroring the existing gtest wrap:

1. Build — build the gmock libraries from the already-fetched googletest tree (build.sh): produce libgmock.a / libgmock_main.a into build/<target>/cpp_libs alongside the gtest libs (gmock's CMake builds both).
2. Link + include — in the Makefile GTEST case, add googlemock/include to INC_DIRS and -lgmock to the link line (before -lgtest).
3. Initialise — call ::testing::InitGoogleMock(&argc, argv) in the UTTestRunner constructor (instead of / in addition to InitGoogleTest), so gmock installs its verification listener and unmet EXPECT_CALLs fail the run.
4. Wrapper header — add include/ut_gmock.h exposing ut-core-styled macros over gmock: UT_MOCK_METHOD, UT_EXPECT_CALL, and thin aliases for the common matchers/actions (UT_ANY/_, UT_RETURN, UT_RETURN_REF, UT_INVOKE, UT_TIMES, UT_AT_LEAST, ...). Pull it in from ut_gtest.h (or ut.h) for the CPP variant.
5. Examples — add mocking example tests under tests/src/cpp_source/ (e.g. ut_test_gmock.cpp): a small abstract interface, a UT_MOCK_METHOD mock, and tests demonstrating expectation setting, matchers, actions (Return/Invoke), cardinality, and a deliberately-unmet expectation (documented/negative case).
6. Docs — update AGENTS.md (§ gtest wrap → add gmock), README.md, and the template/ test example to show mock usage.

Acceptance Criteria

• A user can define a mock of a C++ interface using UT_MOCK_METHOD, set expectations with UT_EXPECT_CALL, and use common matchers/actions — all via UT_-prefixed macros, no direct gmock/gmock.h include required in the test.
• Unmet expectations fail the test run (gmock verification is active).
• The mocking example suite builds and runs under the CPP/gtest variant (./build.sh TARGET=linux VARIANT=CPP or equivalent) and is registered like other suites.
• No regression to the existing gtest wrap or the C/CUnit variant.

Additional Notes

• Complements Feature: Autogenerate gmock mocks + CPP/gtest test skeletons from interface headers #254 (autogeneration of mocks + CPP/gtest skeletons from interface headers) and the existing CPP-autogen issues ut-core : Feature: Add support in auto-generate script to generate CPP tests for GTEST #174 / Task: Autogenerate scripts for generating CPP/gtest tests #161.
• gmock's own gmock_gen.py generator was removed from googletest by 1.15.2 (present up to ~1.10), so mock generation is handled in Feature: Autogenerate gmock mocks + CPP/gtest test skeletons from interface headers #254 via ut-core's own autogenerate scripts, not the upstream script.