ASAN wasn't able to keep track of `boost::coroutine` context switches, and would lead to many false positives being detected. By switching to `boost::coroutine2` and `ucontext`, ASAN is able to know about the context switches advertised by the `boost::fiber` class, which in turn leads to more cleaner ASAN analysis.
This change adds support for sanitizer build options in CI builds workflow. Currently `asan+ubsan` is enabled, while `tsan+ubsan` is left disabled as more changes are required.
