perf: reduce pg_notify call volume by batching together agent metadata updates (#21330)

---------

Signed-off-by: Callum Styan <callumstyan@gmail.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

coderd/coderdtest/coderdtest.go

@@ -55,6 +55,7 @@ import (
 	"cdr.dev/slog/v3/sloggers/slogtest"
 	"github.com/coder/coder/v2/archive"
 	"github.com/coder/coder/v2/coderd"
+	"github.com/coder/coder/v2/coderd/agentapi/metadatabatcher"
 	"github.com/coder/coder/v2/coderd/audit"
 	"github.com/coder/coder/v2/coderd/autobuild"
 	"github.com/coder/coder/v2/coderd/awsidentity"
@@ -171,8 +172,9 @@ type Options struct {
 	SwaggerEndpoint bool
 	// Logger should only be overridden if you expect errors
 	// as part of your test.
-	Logger       *slog.Logger
-	StatsBatcher workspacestats.Batcher
+	Logger                 *slog.Logger
+	StatsBatcher           workspacestats.Batcher
+	MetadataBatcherOptions []metadatabatcher.Option
 
 	WebpushDispatcher                  webpush.Dispatcher
 	WorkspaceAppsStatsCollectorOptions workspaceapps.StatsCollectorOptions
@@ -598,6 +600,7 @@ func NewOptions(t testing.TB, options *Options) (func(http.Handler), context.Can
 			HealthcheckTimeout:                 options.HealthcheckTimeout,
 			HealthcheckRefresh:                 options.HealthcheckRefresh,
 			StatsBatcher:                       options.StatsBatcher,
+			MetadataBatcherOptions:             options.MetadataBatcherOptions,
 			WorkspaceAppsStatsCollectorOptions: options.WorkspaceAppsStatsCollectorOptions,
 			AllowWorkspaceRenames:              options.AllowWorkspaceRenames,
 			NewTicker:                          options.NewTicker,