Feature: Autogenerate gmock mocks + CPP/gtest test skeletons from interface headers

[Ulrond]

Problem/Opportunity

ut-core's autogenerate scripts (scripts/autogenerate.sh, autogenerate_tests.sh, autogenerate_skeletons.sh, autogenerate_shared.sh) today generate compilable C tests from a provided header, but they cannot generate CPP/gtest tests, and they cannot generate gmock mocks for a C++ interface. Unit-testing an abstract C++ interface needs both: a mock of the interface, and a gtest test skeleton that drives it.

Note: GoogleMock's own mock generator (gmock_gen.py, googlemock/scripts/generator/) that historically produced MOCK_METHOD classes from a header was removed from googletest by the pinned 1.15.2 (it existed up to ~1.10). So autogeneration must be provided by ut-core's own tooling rather than the upstream script.

Proposed Solution

Extend ut-core's autogenerate tooling to, given a C++ interface header:

1. Generate a gmock mock class — a UT_MOCK_METHOD entry per pure-virtual method (using the wrappers from Feature: Wrap GoogleMock (gmock) in ut-core with UT_ mocking macros + examples #253).
2. Generate a compilable CPP/gtest test skeleton that instantiates the mock and stubs out UT_ADD_TEST cases — the CPP analogue of today's C-test generation.
3. Reuse the existing skeleton/shared machinery where possible; add a CPP/gtest code path selected by variant or flag.

This subsumes / directly relates to the existing open issues #174 (Add support in auto-generate script to generate CPP tests for GTEST) and #161 (Autogenerate scripts for generating CPP/gtest tests) — the AIDL team has reportedly already used ut-core to generate CPP tests, so liaise on the expected shape.

Acceptance Criteria

• Given a user-provided C++ interface header, the autogenerate script emits:
  • a compilable gmock mock class (one UT_MOCK_METHOD per virtual method, correct signatures/const/override), and
  • a compilable gtest test skeleton referencing that mock and the UT_ macros,
    matching the ergonomics of today's C-test generation.
• Generated output builds under the CPP/gtest variant without hand-editing (skeleton bodies may be TODO stubs).
• Covered by an entry in scripts/test_autogenerate_script.sh.

Additional Notes

• Depends on Feature: Wrap GoogleMock (gmock) in ut-core with UT_ mocking macros + examples #253 (gmock wrap + UT_MOCK_* macros) landing first.
• Consolidates ut-core : Feature: Add support in auto-generate script to generate CPP tests for GTEST #174 and Task: Autogenerate scripts for generating CPP/gtest tests #161 (link/close as appropriate once delivered).
• The bundled googletest parser is unavailable; prefer a lightweight header parse consistent with the current C generator, or a vetted C++ parser — to be decided in design.