Currently testing will only run on pushes to main. This change allows testing on any branch which simplfies testing for forks.
- Use FetchContent to grab googletest - Simplify find_package testing so it's done as a part of ctest - Use the GTest::gtest_main target directly
move pipeline testing from AzDO to GitHub Actions. * update clang versions to 13-15 * update gcc versions to 10-12 * update xcode versions to 14.3.1 and 15.4 * test against C++23 (where supported)