doc: exclude non-API paths and symbols
doc: exclude non-API paths and symbols

The internal namespace, tests, and sample apps interfere with
the framework documentation. Exclude them.
Message-Id: <dedf48cc6b14af8baf3832139aa3f35a0956ea91@scylladb.com>

syuu1228/seastar,cloudius-systems/seastar,scylladb/seastar,scylladb/seastar,scylladb/seastar,syuu1228/seastar,dreamsxin/seastar,syuu1228/seastar,avikivity/seastar,dreamsxin/seastar,avikivity/seastar,avikivity/seastar,dreamsxin/seastar,cloudius-systems/seastar,cloudius-systems/seastar