ci(msys2): add MinGW/UCRT CI matrix and install gtest

[Somsubhra-Nandi]

Description

This PR adds MSYS2-based CI coverage for Windows (MinGW/UCRT/Clang) and installs GoogleTest to ensure MinGW test jobs can run correctly.The change only updates GitHub Actions workflows.

Type of change

• New feature (non-breaking change which adds functionality)

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 (make test or ctest -VV -R <test-name>).
• 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.

[Somsubhra-Nandi]

For reference, the previous PR contained additional skips/guards to get Windows CI from ~10% → 100% while investigating failures.
Here's the link of the closed pr-
#613