Give each tracker agent its own config

The tracker-mapping, common-pattern enrichment, and third-party
disambiguation agents were all built from one shared
TrackerAgentsConfig fed by a single tracker-mapping config slot. That
forced a single AgentTimeout to be reused and patched per worker, and
two unrelated max-turns fields to share one struct.

Split the in-code config into TrackerMappingAgentConfig,
TrackerEnrichmentAgentConfig, and DisambiguationAgentConfig, each with
its own timeout and max-turns, and add dedicated tracker-enrichment and
third-party-disambiguation provider slots (the latter resolving next to
third-party-vetter). Enrichment and disambiguation fall back to the
tracker-mapping slot when their own provider is unset, preserving
single-config deployments.

Drop the shared pkg/agentsbuild package and duplicate its small wiring
into probod and proboctl so the two executables stay decoupled. Wire
the new env vars, builder test coverage, and Helm values.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/cookiebanner/tracker_mapping_agent.go

@@ -76,7 +76,7 @@ type TrackerMappingAgentResult struct {
 }
 
 func buildTrackerMappingAgent(
-	cfg TrackerAgentsConfig,
+	cfg TrackerMappingAgentConfig,
 	pgClient *pg.Client,
 	logger *log.Logger,
 ) *agent.Agent {
@@ -94,7 +94,7 @@ func buildTrackerMappingAgent(
 		panic(fmt.Sprintf("cookiebanner: cannot build tracker identification output type: %s", err))
 	}
 
-	maxTurns := cfg.MappingMaxTurns
+	maxTurns := cfg.MaxTurns
 	if maxTurns < 1 {
 		maxTurns = defaultMappingMaxTurns
 	}