chore(protocol): minor cleanup of ClusterConfig messages; remove DisableTempIndexes option (#10202)

This makes a couple of backwards compatible changes to the
ClusterConfig:

- Remove the `ignore_permissions` and `ignore_delete` booleans which
we've never read or used for anything
- Remove the `disable_temp_indexes` boolean and option entirely. We did
use this one, and about 1% of users have set the option. The only thing
it does is inhibits sending of periodical DownloadProgress messages
while downloading data, which is a minuscule bandwidth optimisation
given that we're already sending data at the time.
- Change the `read_only` boolean (which indicated send-only folders) to
an enum `FolderType`, where the values zero and one match the existing
usage. Again, we don't actually use this value, but I can see that we
might want to and then it makes more sense for it to be more
comprehensive.
- Change the `paused` boolean to an enum `StopReason`, where zero
indicates not stopped and one indicates paused, exactly the same wire
representation as previously but leaves space for additional stop
reasons (errors etc).

lib/config/config_test.go

@@ -1453,11 +1453,10 @@ func TestReceiveEncryptedFolderFixed(t *testing.T) {
 	cfg := Configuration{
 		Folders: []FolderConfiguration{
 			{
-				ID:                 "foo",
-				Path:               "testdata",
-				Type:               FolderTypeReceiveEncrypted,
-				DisableTempIndexes: false,
-				IgnorePerms:        false,
+				ID:          "foo",
+				Path:        "testdata",
+				Type:        FolderTypeReceiveEncrypted,
+				IgnorePerms: false,
 			},
 		},
 	}
@@ -1468,9 +1467,6 @@ func TestReceiveEncryptedFolderFixed(t *testing.T) {
 		t.Fatal("Expected one folder")
 	}
 	f := cfg.Folders[0]
-	if !f.DisableTempIndexes {
-		t.Error("DisableTempIndexes should be true")
-	}
 	if !f.IgnorePerms {
 		t.Error("IgnorePerms should be true")
 	}