refactor: remove vendored Go repos, keep only .proto files

wfe-buildkit-protos/proto/github.com/containerd/ttrpc/request.proto

@@ -0,0 +1,29 @@
+syntax = "proto3";
+
+package ttrpc;
+
+import "proto/status.proto";
+
+option go_package = "github.com/containerd/ttrpc";
+
+message Request {
+	string service = 1;
+	string method = 2;
+	bytes payload = 3;
+	int64 timeout_nano = 4;
+	repeated KeyValue metadata = 5;
+}
+
+message Response {
+	Status status = 1;
+	bytes payload = 2;
+}
+
+message StringList {
+	repeated string list = 1;
+}
+
+message KeyValue {
+	string key = 1;
+	string value = 2;
+}

wfe-buildkit-protos/proto/github.com/containerd/ttrpc/test.proto

@@ -0,0 +1,16 @@
+syntax = "proto3";
+
+package ttrpc;
+
+option go_package = "github.com/containerd/ttrpc/internal";
+
+message TestPayload {
+	string foo = 1;
+	int64 deadline = 2;
+	string metadata = 3;
+}
+
+message EchoPayload {
+	int64 seq = 1;
+	string msg = 2;
+}