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/folderconfiguration.go

@@ -71,7 +71,6 @@ type FolderConfiguration struct {
 	PullerDelayS            float64                     `json:"pullerDelayS" xml:"pullerDelayS" default:"1"`
 	MaxConflicts            int                         `json:"maxConflicts" xml:"maxConflicts" default:"10"`
 	DisableSparseFiles      bool                        `json:"disableSparseFiles" xml:"disableSparseFiles"`
-	DisableTempIndexes      bool                        `json:"disableTempIndexes" xml:"disableTempIndexes"`
 	Paused                  bool                        `json:"paused" xml:"paused"`
 	MarkerName              string                      `json:"markerName" xml:"markerName"`
 	CopyOwnershipFromParent bool                        `json:"copyOwnershipFromParent" xml:"copyOwnershipFromParent"`
@@ -322,7 +321,6 @@ func (f *FolderConfiguration) prepare(myID protocol.DeviceID, existingDevices ma
 	}
 
 	if f.Type == FolderTypeReceiveEncrypted {
-		f.DisableTempIndexes = true
 		f.IgnorePerms = true
 	}
 }