This commit adds a dns refresh counting metric
to the vector_store service. We would like to
track it to make sure that the networking is working
correctly.
The vector store client now supports a comma-separated list of URIs in
the `vector_store_primary_uri` configuration option.
It uses the vector store nodes from these URIs for load balancing and high
availability, querying the next node if the current one fails.
The DNS resolution logic now processes all IP addresses returned in a DNS
response, not just the primary one.
The client will iterate through the list of resolved IPs, attempting to
query the next one if a request fails. This improves high availability
by allowing the client to query other available nodes if one is down.
The DNS resolution logic and its background task are moved out of the
`vector_store_client` and into a new, dedicated class `vector_search::dns`.
This refactoring is the first step towards supporting DNS hostnames
that resolve to multiple IP addresses.
Signed-off-by: Karol Nowacki <karol.nowacki@scylladb.com>
