header: De-bloat schema.hh

The header sits in many other headers, but there's a handy
schema_fwd.hh that's tiny and contains needed declarations
for other headers. So replace shema.hh with schema_fwd.hh
in most of the headers (and remove completely from some).

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Message-Id: <20200303102050.18462-1-xemul@scylladb.com>

db/view/build_progress_virtual_reader.hh

@@ -27,7 +27,7 @@
 #include "mutation_fragment.hh"
 #include "mutation_reader.hh"
 #include "query-request.hh"
-#include "schema.hh"
+#include "schema_fwd.hh"
 #include "tracing/tracing.hh"
 
 #include <boost/range/iterator_range.hpp>