Rename gooni to probe-cli

This is the command I used:
```
rg 'github.com/openobservatory/gooni' --files-with-matches \
    | xargs sed -i '' 's/github.com\/openobservatory\/gooni/github.com\/ooni\/probe-cli/g'
```

nettests/groups/groups.go

@@ -4,12 +4,12 @@ import (
 	"encoding/json"
 
 	"github.com/apex/log"
-	"github.com/openobservatory/gooni/internal/database"
-	"github.com/openobservatory/gooni/nettests"
-	"github.com/openobservatory/gooni/nettests/im"
-	"github.com/openobservatory/gooni/nettests/middlebox"
-	"github.com/openobservatory/gooni/nettests/performance"
-	"github.com/openobservatory/gooni/nettests/websites"
+	"github.com/ooni/probe-cli/internal/database"
+	"github.com/ooni/probe-cli/nettests"
+	"github.com/ooni/probe-cli/nettests/im"
+	"github.com/ooni/probe-cli/nettests/middlebox"
+	"github.com/ooni/probe-cli/nettests/performance"
+	"github.com/ooni/probe-cli/nettests/websites"
 )
 
 // NettestGroup base structure

nettests/im/facebook_messenger.go

@@ -2,7 +2,7 @@ package im
 
 import (
 	"github.com/measurement-kit/go-measurement-kit"
-	"github.com/openobservatory/gooni/nettests"
+	"github.com/ooni/probe-cli/nettests"
 )
 
 // FacebookMessenger test implementation

nettests/im/telegram.go

@@ -2,7 +2,7 @@ package im
 
 import (
 	"github.com/measurement-kit/go-measurement-kit"
-	"github.com/openobservatory/gooni/nettests"
+	"github.com/ooni/probe-cli/nettests"
 )
 
 // Telegram test implementation

nettests/im/whatsapp.go

@@ -2,7 +2,7 @@ package im
 
 import (
 	"github.com/measurement-kit/go-measurement-kit"
-	"github.com/openobservatory/gooni/nettests"
+	"github.com/ooni/probe-cli/nettests"
 )
 
 // WhatsApp test implementation

nettests/middlebox/http_header_field_manipulation.go

@@ -2,7 +2,7 @@ package middlebox
 
 import (
 	"github.com/measurement-kit/go-measurement-kit"
-	"github.com/openobservatory/gooni/nettests"
+	"github.com/ooni/probe-cli/nettests"
 )
 
 // HTTPHeaderFieldManipulation test implementation

nettests/middlebox/http_invalid_request_line.go

@@ -2,7 +2,7 @@ package middlebox
 
 import (
 	"github.com/measurement-kit/go-measurement-kit"
-	"github.com/openobservatory/gooni/nettests"
+	"github.com/ooni/probe-cli/nettests"
 )
 
 // HTTPInvalidRequestLine test implementation

nettests/nettests.go

@@ -7,12 +7,12 @@ import (
 
 	"github.com/apex/log"
 	"github.com/measurement-kit/go-measurement-kit"
-	ooni "github.com/openobservatory/gooni"
-	"github.com/openobservatory/gooni/internal/cli/version"
-	"github.com/openobservatory/gooni/internal/colors"
-	"github.com/openobservatory/gooni/internal/database"
-	"github.com/openobservatory/gooni/internal/output"
-	"github.com/openobservatory/gooni/utils"
+	ooni "github.com/ooni/probe-cli"
+	"github.com/ooni/probe-cli/internal/cli/version"
+	"github.com/ooni/probe-cli/internal/colors"
+	"github.com/ooni/probe-cli/internal/database"
+	"github.com/ooni/probe-cli/internal/output"
+	"github.com/ooni/probe-cli/utils"
 )
 
 // Nettest interface. Every Nettest should implement this.

nettests/performance/dash.go

@@ -2,7 +2,7 @@ package performance
 
 import (
 	"github.com/measurement-kit/go-measurement-kit"
-	"github.com/openobservatory/gooni/nettests"
+	"github.com/ooni/probe-cli/nettests"
 )
 
 // Dash test implementation

nettests/performance/ndt.go

@@ -2,7 +2,7 @@ package performance
 
 import (
 	"github.com/measurement-kit/go-measurement-kit"
-	"github.com/openobservatory/gooni/nettests"
+	"github.com/ooni/probe-cli/nettests"
 )
 
 // NDT test implementation

nettests/websites/web_connectivity.go

@@ -7,7 +7,7 @@ import (
 	"net/http"
 
 	"github.com/measurement-kit/go-measurement-kit"
-	"github.com/openobservatory/gooni/nettests"
+	"github.com/ooni/probe-cli/nettests"
 	"github.com/pkg/errors"
 )