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/golang.org/x/net/http2/timer.go

@@ -0,0 +1,20 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+package http2
+
+import "time"
+
+// A timer is a time.Timer, as an interface which can be replaced in tests.
+type timer = interface {
+	C() <-chan time.Time
+	Reset(d time.Duration) bool
+	Stop() bool
+}
+
+// timeTimer adapts a time.Timer to the timer interface.
+type timeTimer struct {
+	*time.Timer
+}
+
+func (t timeTimer) C() <-chan time.Time { return t.Timer.C }