rclone config redacted: implement support mechanism for showing redacted config

This introduces a new fs.Option flag, Sensitive and uses this along
with IsPassword to redact the info in the config file for support
purposes.

It adds this flag into backends where appropriate. It was necessary to
add oauthutil.SharedOptions to some backends as they were missing
them.

Fixes #5209

backend/filefabric/filefabric.go

@@ -84,6 +84,7 @@ Leave blank normally.
 
 Fill in to make rclone start with directory of a given ID.
 `,
+			Sensitive: true,
 		}, {
 			Name: "permanent_token",
 			Help: `Permanent Authentication Token.
@@ -97,6 +98,7 @@ These tokens are normally valid for several years.
 
 For more info see: https://docs.storagemadeeasy.com/organisationcloud/api-tokens
 `,
+			Sensitive: true,
 		}, {
 			Name: "token",
 			Help: `Session Token.
@@ -106,7 +108,8 @@ usually valid for 1 hour.
 
 Don't set this value - rclone will set it automatically.
 `,
-			Advanced: true,
+			Advanced:  true,
+			Sensitive: true,
 		}, {
 			Name: "token_expiry",
 			Help: `Token expiry time.