perf: websocket grid connectivity for all internode communication (#18461)

This PR adds a WebSocket grid feature that allows servers to communicate via 
a single two-way connection.

There are two request types:

* Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small
  roundtrips with small payloads.

* Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`,
  which allows for different combinations of full two-way streams with an initial payload.

Only a single stream is created between two machines - and there is, as such, no
server/client relation since both sides can initiate and handle requests. Which server
initiates the request is decided deterministically on the server names.

Requests are made through a mux client and server, which handles message
passing, congestion, cancelation, timeouts, etc.

If a connection is lost, all requests are canceled, and the calling server will try
to reconnect. Registered handlers can operate directly on byte 
slices or use a higher-level generics abstraction.

There is no versioning of handlers/clients, and incompatible changes should
be handled by adding new handlers.

The request path can be changed to a new one for any protocol changes.

First, all servers create a "Manager." The manager must know its address 
as well as all remote addresses. This will manage all connections.
To get a connection to any remote, ask the manager to provide it given
the remote address using.

```
func (m *Manager) Connection(host string) *Connection
```

All serverside handlers must also be registered on the manager. This will
make sure that all incoming requests are served. The number of in-flight 
requests and responses must also be given for streaming requests.

The "Connection" returned manages the mux-clients. Requests issued
to the connection will be sent to the remote.

* `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)`
   performs a single request and returns the result. Any deadline provided on the request is
   forwarded to the server, and canceling the context will make the function return at once.

* `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)`
   will initiate a remote call and send the initial payload.

```Go
// A Stream is a two-way stream.
// All responses *must* be read by the caller.
// If the call is canceled through the context,
//The appropriate error will be returned.
type Stream struct {
	// Responses from the remote server.
	// Channel will be closed after an error or when the remote closes.
	// All responses *must* be read by the caller until either an error is returned or the channel is closed.
	// Canceling the context will cause the context cancellation error to be returned.
	Responses <-chan Response

	// Requests sent to the server.
	// If the handler is defined with 0 incoming capacity this will be nil.
	// Channel *must* be closed to signal the end of the stream.
	// If the request context is canceled, the stream will no longer process requests.
	Requests chan<- []byte
}

type Response struct {
	Msg []byte
	Err error
}
```

There are generic versions of the server/client handlers that allow the use of type
safe implementations for data types that support msgpack marshal/unmarshal.

cmd/grid.go

@@ -0,0 +1,83 @@
+// Copyright (c) 2015-2023 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"context"
+	"crypto/tls"
+	"sync/atomic"
+
+	"github.com/minio/minio-go/v7/pkg/set"
+	"github.com/minio/minio/internal/fips"
+	"github.com/minio/minio/internal/grid"
+	xhttp "github.com/minio/minio/internal/http"
+	"github.com/minio/minio/internal/rest"
+)
+
+// globalGrid is the global grid manager.
+var globalGrid atomic.Pointer[grid.Manager]
+
+// globalGridStart is a channel that will block startup of grid connections until closed.
+var globalGridStart = make(chan struct{})
+
+func initGlobalGrid(ctx context.Context, eps EndpointServerPools) error {
+	seenHosts := set.NewStringSet()
+	var hosts []string
+	var local string
+	for _, ep := range eps {
+		for _, endpoint := range ep.Endpoints {
+			u := endpoint.GridHost()
+			if seenHosts.Contains(u) {
+				continue
+			}
+			seenHosts.Add(u)
+
+			// Set local endpoint
+			if endpoint.IsLocal {
+				local = u
+			}
+			hosts = append(hosts, u)
+		}
+	}
+	lookupHost := globalDNSCache.LookupHost
+	if IsKubernetes() || IsDocker() {
+		lookupHost = nil
+	}
+	g, err := grid.NewManager(ctx, grid.ManagerOptions{
+		Dialer:       grid.ContextDialer(xhttp.DialContextWithLookupHost(lookupHost, xhttp.NewInternodeDialContext(rest.DefaultTimeout, globalTCPOptions))),
+		Local:        local,
+		Hosts:        hosts,
+		AddAuth:      newCachedAuthToken(),
+		AuthRequest:  storageServerRequestValidate,
+		BlockConnect: globalGridStart,
+		TLSConfig: &tls.Config{
+			RootCAs:          globalRootCAs,
+			CipherSuites:     fips.TLSCiphers(),
+			CurvePreferences: fips.TLSCurveIDs(),
+		},
+		// Record incoming and outgoing bytes.
+		Incoming: globalConnStats.incInternodeInputBytes,
+		Outgoing: globalConnStats.incInternodeOutputBytes,
+		TraceTo:  globalTrace,
+	})
+	if err != nil {
+		return err
+	}
+	globalGrid.Store(g)
+	return nil
+}