MemorySanitizer reports errors for non-debug builds

Until now, we had run MemorySanitizer instrumented builds based on CMAKE_BUILD_TYPE=Debug and not CMAKE_BUILD_TYPE=RelWithDebInfo, which would be closer to what we release.

There are a few minor errors that cause some tests to fail. Additionally, some Connect and a few Spider tests are failing due to use-of-uninitialized-value. Until now, MemorySanitizer builds on our CI did not cover them. Those bugs should be fixed separately.