chore: add experiment toggle for terraform workspace caching (#20559)

Experiments passed to provisioners to determine behavior. This adds
`--experiments` flag to provisioner daemons. Prior to this, provisioners
had no method to turn on/off experiments.

coderd/provisionerdserver/provisionerdserver.go

@@ -121,6 +121,7 @@ type server struct {
 	NotificationsEnqueuer       notifications.Enqueuer
 	PrebuildsOrchestrator       *atomic.Pointer[prebuilds.ReconciliationOrchestrator]
 	UsageInserter               *atomic.Pointer[usage.Inserter]
+	Experiments                 codersdk.Experiments
 
 	OIDCConfig promoauth.OAuth2Config
 
@@ -182,6 +183,7 @@ func NewServer(
 	enqueuer notifications.Enqueuer,
 	prebuildsOrchestrator *atomic.Pointer[prebuilds.ReconciliationOrchestrator],
 	metrics *Metrics,
+	experiments codersdk.Experiments,
 ) (proto.DRPCProvisionerDaemonServer, error) {
 	// Fail-fast if pointers are nil
 	if lifecycleCtx == nil {
@@ -253,6 +255,7 @@ func NewServer(
 		PrebuildsOrchestrator:       prebuildsOrchestrator,
 		UsageInserter:               usageInserter,
 		metrics:                     metrics,
+		Experiments:                 experiments,
 	}
 
 	if s.heartbeatFn == nil {