* timeout_config
- add `updated_timeout_config` which represents an always-updated
options backed by `utils::updateable_value<>`. this class is
used by servers which need to access the latest timeout related
options. the existing `timeout_config` is more like a snapshot
of the `updated_timeout_config`. it is used in the use case where
we don't need to most updated options or we update the options
manually on demand.
* redis, thrift, transport: s/timeout_config/updated_timeout_config/
when appropriate. use the improved version of timeout_config where
we need to have the access to the most-updated version of the timeout
options.
Fixes#10172
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>