protobuf: remove gogoproto

Removes gogo/protobuf from buildx and updates to a version of
moby/buildkit where gogo is removed.

This also changes how the proto files are generated. This is because
newer versions of protobuf are more strict about name conflicts. If two
files have the same name (even if they are relative paths) and are used
in different protoc commands, they'll conflict in the registry.

Since protobuf file generation doesn't work very well with
`paths=source_relative`, this removes the `go:generate` expression and
just relies on the dockerfile to perform the generation.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

vendor/google.golang.org/grpc/picker_wrapper.go

@@ -20,8 +20,9 @@ package grpc
 
 import (
 	"context"
+	"fmt"
 	"io"
-	"sync"
+	"sync/atomic"
 
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/codes"
@@ -32,35 +33,43 @@ import (
 	"google.golang.org/grpc/status"
 )
 
+// pickerGeneration stores a picker and a channel used to signal that a picker
+// newer than this one is available.
+type pickerGeneration struct {
+	// picker is the picker produced by the LB policy.  May be nil if a picker
+	// has never been produced.
+	picker balancer.Picker
+	// blockingCh is closed when the picker has been invalidated because there
+	// is a new one available.
+	blockingCh chan struct{}
+}
+
 // pickerWrapper is a wrapper of balancer.Picker. It blocks on certain pick
 // actions and unblock when there's a picker update.
 type pickerWrapper struct {
-	mu            sync.Mutex
-	done          bool
-	blockingCh    chan struct{}
-	picker        balancer.Picker
+	// If pickerGen holds a nil pointer, the pickerWrapper is closed.
+	pickerGen     atomic.Pointer[pickerGeneration]
 	statsHandlers []stats.Handler // to record blocking picker calls
 }
 
 func newPickerWrapper(statsHandlers []stats.Handler) *pickerWrapper {
-	return &pickerWrapper{
-		blockingCh:    make(chan struct{}),
+	pw := &pickerWrapper{
 		statsHandlers: statsHandlers,
 	}
+	pw.pickerGen.Store(&pickerGeneration{
+		blockingCh: make(chan struct{}),
+	})
+	return pw
 }
 
-// updatePicker is called by UpdateBalancerState. It unblocks all blocked pick.
+// updatePicker is called by UpdateState calls from the LB policy. It
+// unblocks all blocked pick.
 func (pw *pickerWrapper) updatePicker(p balancer.Picker) {
-	pw.mu.Lock()
-	if pw.done {
-		pw.mu.Unlock()
-		return
-	}
-	pw.picker = p
-	// pw.blockingCh should never be nil.
-	close(pw.blockingCh)
-	pw.blockingCh = make(chan struct{})
-	pw.mu.Unlock()
+	old := pw.pickerGen.Swap(&pickerGeneration{
+		picker:     p,
+		blockingCh: make(chan struct{}),
+	})
+	close(old.blockingCh)
 }
 
 // doneChannelzWrapper performs the following:
@@ -97,27 +106,24 @@ func (pw *pickerWrapper) pick(ctx context.Context, failfast bool, info balancer.
 	var lastPickErr error
 
 	for {
-		pw.mu.Lock()
-		if pw.done {
-			pw.mu.Unlock()
+		pg := pw.pickerGen.Load()
+		if pg == nil {
 			return nil, balancer.PickResult{}, ErrClientConnClosing
 		}
-
-		if pw.picker == nil {
-			ch = pw.blockingCh
+		if pg.picker == nil {
+			ch = pg.blockingCh
 		}
-		if ch == pw.blockingCh {
+		if ch == pg.blockingCh {
 			// This could happen when either:
 			// - pw.picker is nil (the previous if condition), or
-			// - has called pick on the current picker.
-			pw.mu.Unlock()
+			// - we have already called pick on the current picker.
 			select {
 			case <-ctx.Done():
 				var errStr string
 				if lastPickErr != nil {
 					errStr = "latest balancer error: " + lastPickErr.Error()
 				} else {
-					errStr = ctx.Err().Error()
+					errStr = fmt.Sprintf("received context error while waiting for new LB policy update: %s", ctx.Err().Error())
 				}
 				switch ctx.Err() {
 				case context.DeadlineExceeded:
@@ -144,9 +150,8 @@ func (pw *pickerWrapper) pick(ctx context.Context, failfast bool, info balancer.
 			}
 		}
 
-		ch = pw.blockingCh
-		p := pw.picker
-		pw.mu.Unlock()
+		ch = pg.blockingCh
+		p := pg.picker
 
 		pickResult, err := p.Pick(info)
 		if err != nil {
@@ -196,24 +201,15 @@ func (pw *pickerWrapper) pick(ctx context.Context, failfast bool, info balancer.
 }
 
 func (pw *pickerWrapper) close() {
-	pw.mu.Lock()
-	defer pw.mu.Unlock()
-	if pw.done {
-		return
-	}
-	pw.done = true
-	close(pw.blockingCh)
+	old := pw.pickerGen.Swap(nil)
+	close(old.blockingCh)
 }
 
 // reset clears the pickerWrapper and prepares it for being used again when idle
 // mode is exited.
 func (pw *pickerWrapper) reset() {
-	pw.mu.Lock()
-	defer pw.mu.Unlock()
-	if pw.done {
-		return
-	}
-	pw.blockingCh = make(chan struct{})
+	old := pw.pickerGen.Swap(&pickerGeneration{blockingCh: make(chan struct{})})
+	close(old.blockingCh)
 }
 
 // dropError is a wrapper error that indicates the LB policy wishes to drop the