fix: exclude provisioner_state from workspace_build_with_user view (#22159)

The provisioner state for a workspace build was being loaded for every
long-lived agent rpc connection. Since this state can be anywhere from
kilobytes to megabytes this can gradually cause the `coderd` memory
footprint to grow over time. It's also a lot of unnecessary allocations
for every query that fetches a workspace build since only a few callers
ever actually reference the provisioner state.

This PR removes it from the returned workspace build and adds a query to
fetch the provisioner state explicitly.

coderd/database/dbgen/dbgen.go

@@ -504,7 +504,7 @@ func WorkspaceBuild(t testing.TB, db database.Store, orig database.WorkspaceBuil
 			Transition:        takeFirst(orig.Transition, database.WorkspaceTransitionStart),
 			InitiatorID:       takeFirst(orig.InitiatorID, uuid.New()),
 			JobID:             jobID,
-			ProvisionerState:  takeFirstSlice(orig.ProvisionerState, []byte{}),
+			ProvisionerState:  []byte{},
 			Deadline:          takeFirst(orig.Deadline, dbtime.Now().Add(time.Hour)),
 			MaxDeadline:       takeFirst(orig.MaxDeadline, time.Time{}),
 			Reason:            takeFirst(orig.Reason, database.BuildReasonInitiator),