these unused includes are identified by clang-include-cleaner.
after auditing the source files, all of the reports have been
confirmed.
please note, since we have `using seastar::shared_ptr` in
`seastarx.h`, this renders `#include <seastar/core/shared_ptr.hh>`
unnecessary if we don't need the full definition of `seastar::shared_ptr`.
so, in this change, all the unused includes are removed. but there are
some headers which are actually used, while still being identified by
this tool. these includes are marked with "IWYU pragma: keep".
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Spans are more flexible and can be constructed from any contiguous
container (such as small_vector), or a subrange of such a container.
This can save allocations, so change the signature to accept a span.
Spans cannot be constructed from std::initializer_list, so one such
call site is changed to use construct a span directly from the single
argument.
Previously, we moved cql3::functions::function to the
db::functions namespace, since functions are a part of the
data dictionary, which is independent of cql3. We do the
same now for scalar_function, since we wish to make use
of it in a new db::functions::stateless_aggregate_function.
A stub remains in cql3/functions to avoid churn.
