[PLAT-11532] Make affected_node_names and other affected... labels co…

…mma separated to match the description.

Summary: Currently affected_node_names and other similar labels are space separated. Need to make them comma separated to match the description.

Test Plan: Check multiple alerts (disk usage, memory usage, etc), make sure node names are comma separated now

Reviewers: vbansal

Reviewed By: vbansal

Subscribers: sanketh, yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D30534