chore(updater): incorporate FetchServers method in Provider interface

- Each provider interface can now fetch updated servers data
- Rename each provider updater subpackage name to `updater`
- Updater constructor does not take a settings struct
- Updater update method takes in a slice of provider strings

internal/provider/ivpn/updater/api.go

@@ -1,4 +1,4 @@
-package ivpn
+package updater
 
 import (
 	"context"

internal/provider/ivpn/updater/api_test.go

@@ -1,4 +1,4 @@
-package ivpn
+package updater
 
 import (
 	"context"

internal/provider/ivpn/updater/mocks_generate_test.go

@@ -1,3 +1,3 @@
-package ivpn
+package updater
 
 //go:generate mockgen -destination=mocks_test.go -package $GOPACKAGE . Warner

internal/provider/ivpn/updater/mocks_test.go

@@ -2,7 +2,7 @@
 // Source: github.com/qdm12/gluetun/internal/provider/ivpn/updater (interfaces: Warner)
 
 // Package ivpn is a generated GoMock package.
-package ivpn
+package updater
 
 import (
 	reflect "reflect"

internal/provider/ivpn/updater/resolve.go

@@ -1,4 +1,4 @@
-package ivpn
+package updater
 
 import (
 	"time"

internal/provider/ivpn/updater/roundtrip_test.go

@@ -1,4 +1,4 @@
-package ivpn
+package updater
 
 import "net/http"
 

internal/provider/ivpn/updater/servers.go

@@ -1,6 +1,6 @@
-// Package ivpn contains code to obtain the server information
+// Package updater contains code to obtain the server information
 // for the Surshark provider.
-package ivpn
+package updater
 
 import (
 	"context"

internal/provider/ivpn/updater/servers_test.go

@@ -1,4 +1,4 @@
-package ivpn
+package updater
 
 import (
 	"context"

internal/provider/ivpn/updater/updater.go

@@ -1,4 +1,4 @@
-package ivpn
+package updater
 
 import (
 	"net/http"