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
Unfortunately 404 test was not consistent and non-trivial to adapt. I also couldn’t get the validation tests to work well either. Revisit if we have time to dig deeper into spring.
Otherwise it can interfere with the more common Servlet instrumentation (changing the root span name).
Unify attribute/property name for saving span on a request/context.
Also add tests for embedded GlassFish.
This ensures that `dd-tracng-ot` gets included into shadow jar.
Before this patch it was included only 'by accident' via some
transitive dependencies of some instrumentations.