Query WOODPECKER_AGENT_SECRET from API

[windsource]

With #5 an new parameter PICUS_WOODPECKER_AGENT_IDbecomes mandatory which also allows to query the Woodpecker API for agent data including the token.

Do not require to pass PICUS_AGENT_WOODPECKER_AGENT_SECRET for hcloud agents anymore but use the Woodpecker API to query that value.

For implementation a new client could be created, that contains all API access and structures to woodpecker including the queue/info API.