deps: update protobuf

The module we used previouly, github.com/golang/protobuf/proto, is
deprecated. See https://github.com/golang/protobuf/releases/tag/v1.5.2
and golang/protobuf#1306.

We use the official succssor:

```
(fix imports)
go get google.golang.org/protobuf/proto@v1.28.1
go mod tidy
```

The .pb.go generated files also needed to be updated with an updated
protoc-gen-go:

```
go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.28.1
```

A new script was added to generate the files, as the
`import_path=messages` flag seems to be removed in favour of the `M`
flag, which unfortunately has to be specified for each .proto file :(

README.md

@@ -7,11 +7,15 @@ tagging versions.
 
 Clone the [BitBox02 firmware repo](https://github.com/digitalbitbox/bitbox02-firmware):
 
+Make sure you have `protoc` and
+[protoc-gen-go](https://developers.google.com/protocol-buffers/docs/reference/go-generated)
+installed:
+
 `git clone https://github.com/digitalbitbox/bitbox02-firmware.git`
 
 ```sh
 rm -rf api/firmware/messages/*
 cp /path/to/bitbox02-firmware/messages/*.proto api/firmware/messages/
 rm api/firmware/messages/backup.proto
-go generate ./...
+./api/firmware/messages/generate.sh
 ```

api/firmware/btc.go

@@ -24,7 +24,7 @@ import (
 	"github.com/digitalbitbox/bitbox02-api-go/api/firmware/messages"
 	"github.com/digitalbitbox/bitbox02-api-go/util/errp"
 	"github.com/digitalbitbox/bitbox02-api-go/util/semver"
-	"github.com/golang/protobuf/proto"
+	"google.golang.org/protobuf/proto"
 )
 
 const multisigNameMaxLen = 30

api/firmware/btc_test.go

@@ -20,8 +20,8 @@ import (
 
 	"github.com/digitalbitbox/bitbox02-api-go/api/firmware/messages"
 	"github.com/digitalbitbox/bitbox02-api-go/util/semver"
-	"github.com/golang/protobuf/proto"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
 )
 
 const hardenedKeyStart = 0x80000000

api/firmware/device.go

@@ -27,8 +27,6 @@ import (
 	"github.com/flynn/noise"
 )
 
-//go:generate sh -c "protoc --proto_path=messages/ --go_out='import_path=messages,paths=source_relative:messages' messages/*.proto"
-
 var (
 	lowestSupportedFirmwareVersion                   = semver.NewSemVer(9, 0, 0)
 	lowestSupportedFirmwareVersionBTCOnly            = semver.NewSemVer(9, 0, 0)

api/firmware/device_test.go

@@ -25,8 +25,8 @@ import (
 	"github.com/digitalbitbox/bitbox02-api-go/api/firmware/mocks"
 	"github.com/digitalbitbox/bitbox02-api-go/util/semver"
 	"github.com/flynn/noise"
-	"github.com/golang/protobuf/proto"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
 )
 
 // newDevice creates a device to test with, with init/pairing already processed.