MINOR: sym: use the symbol table to resolve a DSO name

MINOR: sym: use the symbol table to resolve a DSO name

resolve_dso_name() only used dladdr() to find the object containing an
address. Our in-process symbol table also knows the owning object, is
lock-free and async-signal-safe, and also works on static builds where
dladdr() may not. Try it first and keep dladdr() as a fallback for
addresses that are not covered by any symbol, or when the table has not
been built yet.