github: Enable AddressSanitizer if leak-detective is disabled
At least for the tests where it is available and works. It conflicts
with the instrumentation used by the coverage and fuzzing (and possibly
sonarcloud) tests, the toolchain for the Windows builds doesn't seem to
support it, and on FreeBSD the test executables hang due to a
compatibility issue with FreeBSD's qsort(), which has been fixed [1],
but that has not made it into the clang version in the base system.
For the custom OpenSSL build, debug symbols are enabled so we can
suppress some leaks properly.