Allow to configure agent

[meyayl]

As a user of bivac, I would like to be able to configure the agent, so that I can configure the deployment according constraints in my cluster.

Since there seem to be no way to configure the agent, the enforced resource quota prevents the agents from starting:

time="2023-12-19T16:15:28Z" level=error msg="failed to backup volume: failed to deploy agent: failed to create agent: pods \"bivac-agent-zvz6c\" is forbidden: failed quota: default-quota: must specify cpu for: bivac-agent; memory for: bivac-agent" hostname=random-host try=1 volume=random-volume