ci(msys2): enable MinGW/UCRT/Clang CI with GTest

[Somsubhra-Nandi]

Description

This PR enables MSYS2 CI coverage for Windows (MinGW, UCRT, and Clang) and fixes MSYS2 test build failures by explicitly installing GoogleTest in the MSYS2 environment.

On MSYS2, GoogleTest is not available by default, which causes test binaries to fail at link time due to a missing libgtest.a. Installing GTest directly in the CI job unblocks the MSYS2 builds and makes the CI matrix reliable.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Documentation update

Checklist:

• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests/screenshots (if any) that prove my fix is effective or that my feature works.
• I have tested the tests implicated (if any) by my own code and they pass (via CI).
• If my change is significant or breaking, I have passed all tests with ./docker-compose.sh test &> output and attached the output.
• I have tested my code with OPTION_BUILD_ADDRESS_SANITIZER or ./docker-compose.sh test-address-sanitizer &> output and OPTION_TEST_MEMORYCHECK.
• I have tested my code with OPTION_BUILD_THREAD_SANITIZER or ./docker-compose.sh test-thread-sanitizer &> output.
• I have tested with Helgrind in case my code works with threading.
• I have run make clang-format in order to format my code and my code follows the style guidelines.