Support multiple data sources

[dmartinol]

The thv-registry-api must support the configuration of mulriple data sources instead of just one.

• Each data source has its own type and configuration

sources:
  - name: thv  
    type: configmap
    format: toolhive
    configmap:
      name: auto-sync-registry-data
      key: registry.json
    syncPolicy:
      interval: "30m"  # Automatically sync every 30 minutes
  - name: another
    type: git
    ...

• The manual sync annotation and API must have the option to indicate a single data source to update

# Sync a  single data source
toolhive.stacklok.dev/sync-trigger:<SOURCE_NAME>
# Sync all data source
toolhive.stacklok.dev/sync-trigger

# Sync a  single data source
PUT /registry/sync?source=thv
# Sync all data source
PUT /registry/sync