Zoekt: Initial reallocation task implementation

Background

This is a corrective action from 2024-04-02: Zoekt disk usage saturation (gitlab-com/gl-infra/production#17770 - closed)

Proposal

We should turn the script into a scheduling task so that we don't need to babysit the nodes.

We can start using 2 watermark limits 0.7 and 0.8. The low one is going to be used for assigning namespaces and the second one for avicting namespaces.