Get connected agents by a list of agent/project ids

Follow-up for !69820 (comment 672902822).

New API: get connected agents by a list of agen... (gitlab-org/cluster-integration/gitlab-agent#158 - closed) introduced new gRPC methods that enable to get connected agents by a list of agent IDs and project IDs. Current implementation would call multiple times for each project. We can decrease the number of requests sent to KAS by leveraging this new gRPC methods.

Proposal

• Update Ruby gem version of kas-grpc
• Use GetConnectedAgentsByProjectIds and / or GetConnectedAgentsByAgentIds gRPC methods to get connected agents