[Feature]: ResourceStatusSystem (RSS) in diracx

### User Story

**As a** diracx developer
**I want** to port the minimal subset of RSS in diracx
**So that** several other developments can proceed, as RSS is central to many of them

**As a** Dirac(X) administrator
**I do not** need nodes information
**As** Sites and resources are enough

**As a** diracx developer
**I want** to port the policy decisions and enforcement of RSS in diracx
**So that** I can remove it from legacy DIRAC

**As a** Dirac(X) administrator
**I want** to enable RSS within diracx
**So that** I can disable RSS from legacy DIRAC

**As a** Dirac(X) administrator
**I want** to keep the possibility of enabling policies or not
**So that** I can keep the system as simple as possible

**As a** developer of a diracx extension
**I want** to define my own policies
**So that** I can customize the list of them

**As a** Dirac(X) administrator
**I want** to manually insert downtime schedule
**So that** I can insert also those that do not appear on GOCDB

**As a** Dirac(X) administrator
**I want** sensible defaults
**So that** I do not have to bother with configuration if I do not want to

**As a** Dirac(X) administrator
**I want** to see a clear relation between sites and resources

**As a** Dirac(X) administrator
**I want** job draining before a downtime, rather than sudden banning

**As a** Dirac(X) administrator
**I want** to see pledged resources, maximum resource allowance, resource usage

### Feature Description

This feature request should be considered as an "epic" from which several tasks will be derived. The user stories are derived from questionnaire https://docs.google.com/forms/d/e/1FAIpQLSd3r-ysd-pvneMK-aRm8aAtOjXg-qFiZvyLlyTzBKReWt1byQ/viewform?usp=sharing&ouid=117871612314528955780

### Definition of Done

_No response_

### Alternatives Considered

_No response_

### Related Issues

_No response_

### Additional Context

_No response_