Replacing Advice.class references with string construction.
This stops the JVM from loading the Advice classes which are used as templates for byte buddy and doesn't ever need to be run directly.
This eliminates ~130 class loads at start-up -- and saves 0.5MiB in metaspace
Previously we were inheriting from the parent and also often setting as a tag.
Apply default span assertion to verify the spanType is being checked properly. (Include error state too.)