Request Limiter Reload tests (#25126)

This PR introduces a new testonly endpoint for introspecting the
RequestLimiter state. It makes use of the endpoint to verify that changes to
the request_limiter config are honored across reload.

In the future, we may choose to make the sys/internal/request-limiter/status
endpoint available in normal binaries, but this is an expedient way to expose
the status for testing without having to rush the design.

In order to re-use as much of the existing command package utility funcionality
as possible without introducing sprawling code changes, I introduced a new
server_util.go and exported some fields via accessors.

The tests shook out a couple of bugs (including a deadlock and lack of
locking around the core limiterRegistry state).

command/server_test.go

@@ -22,11 +22,9 @@ import (
 	"testing"
 	"time"
 
-	"github.com/hashicorp/cli"
 	"github.com/hashicorp/vault/command/server"
 	"github.com/hashicorp/vault/helper/testhelpers/corehelpers"
 	"github.com/hashicorp/vault/internalshared/configutil"
-	"github.com/hashicorp/vault/sdk/physical"
 	physInmem "github.com/hashicorp/vault/sdk/physical/inmem"
 	"github.com/hashicorp/vault/vault"
 	"github.com/hashicorp/vault/vault/seal"
@@ -97,29 +95,6 @@ cloud {
 `
 )
 
-func testServerCommand(tb testing.TB) (*cli.MockUi, *ServerCommand) {
-	tb.Helper()
-
-	ui := cli.NewMockUi()
-	return ui, &ServerCommand{
-		BaseCommand: &BaseCommand{
-			UI: ui,
-		},
-		ShutdownCh: MakeShutdownCh(),
-		SighupCh:   MakeSighupCh(),
-		SigUSR2Ch:  MakeSigUSR2Ch(),
-		PhysicalBackends: map[string]physical.Factory{
-			"inmem":    physInmem.NewInmem,
-			"inmem_ha": physInmem.NewInmemHA,
-		},
-
-		// These prevent us from random sleep guessing...
-		startedCh:         make(chan struct{}, 5),
-		reloadedCh:        make(chan struct{}, 5),
-		licenseReloadedCh: make(chan error),
-	}
-}
-
 func TestServer_ReloadListener(t *testing.T) {
 	t.Parallel()