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).

proto/bep/bep.proto

@@ -47,11 +47,9 @@ message ClusterConfig {
 message Folder {
   string id = 1;
   string label = 2;
-  bool read_only = 3;
-  bool ignore_permissions = 4;
-  bool ignore_delete = 5;
-  bool disable_temp_indexes = 6;
-  bool paused = 7;
+  FolderType type = 3;
+  FolderStopReason stop_reason = 7;
+  reserved 4 to 6;
 
   repeated Device devices = 16;
 }
@@ -75,6 +73,18 @@ enum Compression {
   COMPRESSION_ALWAYS = 2;
 }
 
+enum FolderType {
+	FOLDER_TYPE_SEND_RECEIVE = 0;
+	FOLDER_TYPE_SEND_ONLY = 1;
+	FOLDER_TYPE_RECEIVE_ONLY = 2;
+	FOLDER_TYPE_RECEIVE_ENCRYPTED = 3;
+}
+
+enum FolderStopReason {
+  FOLDER_STOP_REASON_RUNNING = 0; // i.e., not stopped
+  FOLDER_STOP_REASON_PAUSED = 1;
+}
+
 // Index and Index Update
 
 message Index {