crimson: avoid seastar::do_with() due to performance reasons.

crimson: avoid seastar::do_with() due to performance reasons.

`seastar::do_with(T&& rvalue, F&& f) takes object for lifetime
extension by rvalue reference. This imposes materialization of
a temporary to move from even when `do_with()` is being called
like:

  `do_with(OpsExecuter{...}, [] { /* ... */)`.

The reason behind that is following language rule:

  "Temporary objects are created when a prvalue is materialized
  so that it can be used as a glvalue, which occurs (since C++17)
  in the following situations:

   * binding a reference to a prvalue"
  (from: "Temporary object lifetime", cppreference.com)

As OpsExecuter is pretty heavy-weight, it is reasonable to avoid
`do_with()` and perform the lifetime extension with smart pointer.
Additional benefit is squeezing plain-to-errorated conversion in
`seastar::internal::do_with_state::get_future()`.

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>