chore(all): provider to servers map in allServers

- Simplify formatting CLI
- Simplify updater code
- Simplify filter choices for config validation
- Simplify all servers deep copying
- Custom JSON marshaling methods for `AllServers`
- Simplify provider constructor switch
- Simplify storage merging
- Simplify storage reading and extraction
- Simplify updating code

internal/storage/hardcoded_test.go

@@ -3,6 +3,8 @@ package storage
 import (
 	"testing"
 
+	"github.com/qdm12/gluetun/internal/constants/providers"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -12,5 +14,13 @@ func Test_parseHardcodedServers(t *testing.T) {
 	servers, err := parseHardcodedServers()
 
 	require.NoError(t, err)
-	require.NotEmpty(t, len(servers.Cyberghost.Servers))
+
+	// all providers minus custom
+	allProviders := providers.All()
+	require.Equal(t, len(allProviders), len(servers.ProviderToServers))
+	for _, provider := range allProviders {
+		servers, ok := servers.ProviderToServers[provider]
+		assert.Truef(t, ok, "for provider %s", provider)
+		assert.NotEmptyf(t, servers, "for provider %s", provider)
+	}
 }