code: Reduce tracing/*hh fanout

There are some headers that include tracing/*.hh ones despite all they
need is forward-declared trace_state_ptr

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>

Closes #14155

db/view/build_progress_virtual_reader.hh

@@ -14,13 +14,14 @@
 #include "mutation/mutation_fragment.hh"
 #include "query-request.hh"
 #include "schema/schema_fwd.hh"
-#include "tracing/tracing.hh"
 
 #include <boost/range/iterator_range.hpp>
 
 #include <iterator>
 #include <memory>
 
+namespace tracing { class trace_state_ptr; }
+
 namespace db::view {
 
 // Allows a user to query the views_builds_in_progress system table